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1 , m . 

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;-- HI 







Graduate of the School of Physics and "iomreat" of the Conservatoire National 
Chemistry of the City of Paris des Arts et Metiers 

and of the Pasteur Institute Director of Works 




Physiological Chemist, Bureau of Chemistry, Department of Agriculture 
Washington, D. C. 








Copyright, 1906 




THE publication of Robine and Lenglen's "L'lndustrie des 
Cyanures" in the series Encyclopedic Industrielle in France is a 
good indication of the value of the work. 

The translation of this book into English makes more accessible 
to the American worker in Industrial Chemistry the many and 
various processes proposed for the production of cyanide compounds, 
and should be a help in stirring him to greater endeavor along 
these lines. 

The Index, rarely found in French books, has been added by 
the translator, and at his suggestion the publishers have appended 
Dr. Chas. E. Munroe's brochure on " Precious Metals Recovered by 
Cyanide Processes" which recently appeared as a publication of the 
U. S. Dept. of Commerce and Labor. 

The translator, being moreover interested in Agricultural Chem- 
istry, dares to hope that one of the results of this translation will 
be the successful fixation of atmospheric nitrogen on an industrial 

WASHINGTON, January, 1906. 






GENERAL CONSIDERATIONS ..................... . 



Cyanogen. .: ................................................... . 10 

Paracyanogen ................................................... 13 

Hydrocyanic Acid ............................................... 14 

Metallic Cyanides ..... ........................................... 18 

Potassium Cyanide ......................................... 20 

Sodium Cyanide ........................................... 23 

Ammonium Cyanide ....................................... 23- 

Calcium Cyanide ........................................... 24 

Barium Cyanide ........................................... 24 

Aluminium Cyanide ................................... ..... 24 

Iron Cyanide ........................................... ... 25 

Chromium Cyanide .......................... .............. 25 

Manganese Cyanide ........................................ 25 

Tin Cyanide ............................................... 25 

Lead Cyanide ............................................. 25- 

Copper Cyanide ........................................... 26 

Mercury Cyanide .......................................... 26 ; 

Silver Cyanide ............................................. 26 

Cobalt Cyanide ............................ . ............... 27 

Nickel Cyanide ...................... . ..................... 27 

Gold Cyanide ............................................. 27 

Platinum Cyanide ............. ............................ 27 

Double Cyanides ................................................. 28 

Ferrocyanides. Potassium Ferrocyanide ..................... 29 

Ferricyanides ............................................. 32 




Cobalticyanides 34 

Manganocyanides. . 34 

Platinocyanides 34 

Aurocyanides 35 

/ Nitroprussiates 35 

Oxygen Compounds of Cyanogen 36 

\s Cyanic Acid 36 

Potassium Cyanate 36 

Cyanuric Acid and Tricyanates 37 

Sulphocyanides 37 

Potassium Sulphocyanide 38 

Organic Compounds 39 

, Nitriles and Carbylamines 39 

v Cyanic Esters 40 




I. Analytical Properties 42 

Hydrocyanic Acid 42 

Cyanides. . . 42 

Ferrocyanides 43 

Ferricyanides 43 

Sulphocyanides 43 

Cyanates 44 

II. Methods for the Analysis of the Various Cyanide Compounds. . 44 

Cyanides 44 

Liebig's Method 44 

Fordos and Gelis' Method 45 

Analysis of Commercial Potassium Cyanide 47 

O. Hertig's Process 47 

Determination of Medicinal Hydrocyanic Acid in Dis- 
tillates of Bitter Almonds and Laurel Cherry (Bui- 

gnet Method) 48 

Ferrocyanides 49 

Sulphocyanides 50 

Determination of Ferrocyanides in the Purifying Materials of 

Illuminating-gas 50 

Knublauch's Method 50 

Moldenhauer and Leybold's Method. 51 

Burschell's Method ^ 52 

Zaloziecki's Method 52 

Donath and Margosches' Method. 53 

Determination of Prussian Blue in the Spent Oxids 54 

Method of Nauss of the Carlsruhe Gas Works 54 

Toxicological Research 54 





I. Cyanogen 56 

II. Hydrocyanic Acid 57 

III. Potassium Cyanide 58 

IV. Ammonium Cyanhydrate 60 

V. Potassium Ferrocyanide . . ."T 60 

VI. Potassium Cyanate 66 








I. Non-synthetic Processes 85 

A. Extraction of Cyanides from Ferrocyanides 85 

Old Process 85 

Liebig's Process 87 

Wagner's Process .88 

Chaster' s Process 88 

Rossler and Hasslacher's Process 89 

Wichmann and Vautin's Process 90 

Dalinot's Process 92 

Adler's Process 93 

Etard's Process .' . . 94 

Bergmann's Process 94 

B. Extraction of Cyanides from Sulphocyanides 95 

I. By Oxidation 96 

Raschen's Process 97 

Beringer's Process 101 

II. By Reduction 102 

Playfair's Process 102 



Hans Luttke's Process. . . , 104 

British Cyanide Co.'s Process 105 

Hetherington and Musspratt's Process 106 

Process of the Silesia Verein Chemische Fabrik. . . . 107 

Goerlich and Wichmann's Process 107 

Bower's Process 107 

Conroy's Process 108 

Rasfchen, Davidson, and Brock's Process 110 

Etard's Process 110 

Finlay's Process 110 

II Synthetic Processes General Remarks Ill 

A. Processes Utilizing Atmospheric Nitrogen 117 

Bunsen's Process 123 

Possoz and Boissiere' s Process 124 

Newton's Process 126 

Blair's Process 126 

Armengaud's Process! 126 

Marguerite and Sourdeval's Process 126 

Mond's Process. . 127 

Weldon's Process 128 

Fogarty's Process 128 

Dickson's Process 129 

Lambilly's Process 129 

Gilmour's Process 134 

Young's Process. . . 134 

Mackey's Process 135 

Readmann's Process 135 

Mehner's Process 137 

Swan and Kendall's Process 137 

Pestchow's Process 137 

Chipmann's Process 138 

Moi'se and Mehner's Process 140 

Castner's Process 141 

Hornig and Schneider's Process 143 

Mehner's Process 143 

Frank and Caro's Process 144 

Process of the Chemische Fabrik Pfersee, Augsburg 149 

Berniger, Wolfram and Blackmore's Process 150 

Dziuk's Process 1 50 

Process of the General Electro-Chemical Co 152 

B. Processes Utilizing Ammonia 1 53 

Lance and Bourgade's Process 156 

Mactear's Process 157 

Stassfurter Chemische Fabrik' s Process 158 

Moulis and Sar's Process 160 

Lambilly's Process 161 

Beilby's Process 162 

Young and Macfarlane's Process 1 63 



Chaster' s Process 165 

Pleger's Process 165 

Roca's Process. ^ 166 

Hood and Salamon's Process 169 

Hornig's Process 170 

Schneider's Process 171 

Castner's Process 172 

Process of the Deutsche Gold u. Silber Sheide Anstalt 175 

Lambilly's Process 178 

Martin's Process. 179 

Clock's Process 179 

Huntington's Process 180 

Hoyermann's Process 180 

Roussin Process 181 

Kerp's Process 181 

Kellner's Process 182 

Grossmann's Process 182 

III. Special Processes 183 

Process of the Chemische Fabrik Aktiengesellschaft 183 

Vidal's Process 184 

Bueb's Process 185. 

Ortlieb and Miiller's Process .170 



I. Old Processes, Based on the Use of Nitrogenous Organic Substances 193 

Calcination or Production of Metal : 197 

Engler's Apparatus . 201 

Theory of the Manufacture of Ferrocyanide of Potassium by the 

Old Process. 205 

Yield 207 

Lixiviation and Crystallization 210 

BrunquelPs Process 210 

Karmrodt's Process 211 

Conroy's Process 212 

Musspratt's Process 212 

Goerlich and Wichmann's Process 213 

Process of the Castelet Works 213 

II. Extraction of Cyanide Compounds from Illuminating-gas and its 

Residues 214 

A. Direct Extraction from Gas 229 

Knublauch's Process 231 

Gasch's Process 232 

Rowland's Process 233 

Fowlis' Process 233 

Clauss and Domeier's Process 234 

Schroeder's Process. . 234 



Teichmann's Process 235 

Lewis' Process 236 

Bueb Process 237 

Feld's process 241 

B. Extraction of Cyanogen Compounds from the Ammoniacal 
Liquors 242 

Pendrie's Process 242 

Bower's Process 243 

Lewis' Process 243 

C. Extraction of Cyanogen Compounds from the Purifying 
Materials 245 

Gauthier-Bouchard's Process 248 

Valentin's Process 256 

Harcourt's Process 257 

Kunheim's Process 257 

Hempel's Process 257 

Wolfram's Process 257 

Donath's Process 258 

Richter's Process 258 

Esop's Process 258 

Marasse's Process 258 

Holbling's Process 259 

Lewis' Process 259 

Mascow's Process 259 



The Chlorine Process. . . i 261 

Reichardt's Process 263 

Process of the Bouxvillers Mines 264 

Dubosc's Process 265 

Process of the Deutsche Gold und Silber Sheide Anstalt 265 

Kassner's Process. 266 

Carl Beck's Process 267 

Williamson's Process 267 



Geli's Process 270 

Deiss and Monnier's Process 281 

Hood and Salamon's Process 282 

Brock's Process 282 

British Cyanides Co.'s Process \ 283 

Albright's Process 285 

Tcherniac Process 285 

Goerlich and Wichmann's Process 286 





Soluble Prussian Blue 292 

Turnbull's Blue 292 

Monthier's Blue or Ammoniacal Prussian Blue 292 

Antimony Blue 293 






INDEX 403 



Chemical industries are in a high degree artificial and progressive. 

(BERTHELOT: Opening speech at the International Congress 
of Chemistry, Paris, 1900.) 

IF the condition of chemical industry at the beginning and at 
the end of the nineteenth century be compared, one is immediately 
impressed with the immense progress which has been accomplished. 

Chemical industry, at the beginning, being for the most part 
based on a more or less crude empiricism, could not hope for better 
results than those brought about either through accident or through 
long experience. 

Gradually, the rational study of reactions, and the adaptation 
of purely scientific ideas and discoveries to manufacturing, made 
it necessary to have, as the basis of each modus operandi, a pro- 
found theoretical knowledge. From that moment advance in 
industrial chemistry was rapid and to-day, also, it is intimately 
bound to the progress of scientific research; it is the immediate 
result of it. 

Among the scientific discoveries which have had a great effect 
on the progress of industrial chemistry, those which especially relate 
to the synthesis of bodies should be mentioned. It is, in fact, due 
to synthesis that numerous compounds, which, till then, nature 
alone was thought capable of producing, have been successfully 
reproduced. The processes for the manufacture of certain products 
have been greatly simplified, and consequently the net cost con- 
siderably reduced through the industrial adaptation of this principle. 


The cyanide industry, which is to be studied in this work, has 
not escaped this general law. 

The happy discovery of Scheele, who was the first to obtain 
Prussian blue, was the starting-point of this industry. Later, potas- 
sium ferrocyanide was prepared by the calcination of nitrogenous 
materials in the presence of alkali carbonates, and although this 
modus operand! was absolutely empirical, it sufficed, for a long 
time, for the limited demand. It is probable that this state of 
affairs would have existed even to-day had not the use of potassium 
cyanide in the metallurgy of gold given to this industry such an 
impetus that the manufacture of cyanide compounds has made 
remarkably rapid development. 

The application of cyanides to the treatment of auriferous mate- 
rials, which dates bacjc about fifteen years, is therefore the imme- 
diate .cause of the progress realized. Foreseeing the great role the 
new industry was to play, manufacturers and investigators eagerly 
sought out every improvement possible. 

It should, however, be stated that long before not altogether 
successful attempts had been made to modify the old processes. 

In the mean time, the discovery of cyanide compounds in the 
purifying materials used in the manufacture of illuminating-gas 
had likewise opened up the field of investigation toward synthetic 
processes, but only in individual cases, although very interesting 
in themselves. 

The early investigations were unquestionably valuable, and 
those which relate particularly to synthetic production were the 
starting-point for many researches. This is the tendency of the 
times; and either in the hope of a simpler manufacture or of approach- 
ing as close as possible to the theoretical side of the question, we 
shall see that the synthetic processes for the manufacture of cyanides 
are now preeminent. These are the processes which in all proba- 
bility should produce the best results, and should solve the prob- 
lem satisfactorily from an economical as well as an industrial point 
of view. 

The study of this special field of industrial chemistry is there- 
fore of great interest. Having been occupied for many years with 
the different questions relating thereto, we find no special works 
on this subject, at least in France. 


These reasons led us to bring together in an appropriate didactic 
order all the documents on this subject which we have been able 
to collect in the course of our researches; such is the genesis of the 
work which we present to the public. 

The work divides itself into four parts: 
Part I. Chemistry of cyanogen and its derivatives. 
Part II. The present condition of the cyanide industry. Com- 
mercial and industrial study. 

Part III. Methods for the manufacture of cyanide compounds. 
Part IV. Application of the various cyanide compounds. 




BY cyanogen combinations is meant all compounds containing 
the radical CN. 

This radical is derived from several sources. It may arise from 
the direct union of carbon .and of nitrogen, which union produces 
cyanogen CN; or it may arise by addition or substitution from 
compounds, such as amides, imides, or amines, whose real radical 
is C or CO. 

The radical CN may therefore be related to two classes of com- 
pounds: first, to true cyanogen compounds; second, to isomers of 
the first class, which isomers contain the same elements in quan- 
titative proportions; the former differ, however, from the latter 
from the point of view of their chemical constitution, and are 
endowed with different and peculiar properties. 

The formation of cyanogen and of its derivatives, its constitu- 
tion and the determination of its valency have all been the object of 
much research, and although these various points have not yet been 
definitely solved, the results of these various studies allow the question 
to be thus considered: Carbon, a tetratomic element, is saturated 
by means of the free nitrogen valencies.- This latter is sometimes 
triatomic, and sometimes pentatomic. In the latter case three of its 


valencies are different from the other two. It follows that the carbon 
may therefore satisfy three of its valencies; the compound thus 
formed will have three free bonds, one attached to the carbon and two 
to the nitrogen. The constitution of cyanogen may therefore, from 
these considerations, be represented by the formula -C=N = . 

This constitution of cyanogen allows some of its properties to 
be at once foreseen. If the nitrogen be replaced by elements of 
the same atomic value, the original compound becomes transformed 
into a more carbonaceous one. On the other hand, if the radical CN 
is connected with an alcoholic radical, the union takes place through 
the carbon atom. Moreover, Gautier, Wurtz, Limpricht, and Cloez 
admit that cyanogen is trivalent, for they succeeded in forming 
the union of hydrocyanic acid and of its esters with the haloid 
acids. The question of the formation of cyanogen and its com- 
pounds is far from being solved. It has been the object of much 
dispute, and deep study has not given sanction to one theory more 
than to another. 

The various methods by which this formation may be explained 
are based, rather, on probabilities than upon real data and an exact 
knowledge of the phenomena produced. 

Nevertheless, this question is worthy of attention from more 
than one point of view. No doubt the discovery of the true method 
of the formation of the cyanogen compounds would bring about, 
as an immediate result, the proper process of manufacturing these 
same compounds. Therefore it may not be useless, at the beginning 
of this work, to give some idea of the theory of " cyanides," and, 
without attempting to establish it in a definite manner, to give 
the pros and cons of each of the theories propounded. 

It is known that the radical CN cannot be formed through a 
direct union; it is formed, however, whenever C and N are found 
in the presence of an alkali at a high temperature: then there is 
formed a cyanogen compound in which the group CN is found 
united to the alkali metal. This reaction takes place according 
to the general formula 

C+N+M = CNM. 

This reaction, or rather the formation of the group CN, may 
be explained in several ways; in favor of each theory strong but 


refutable argument may be presented. The various ways of con- 
sidering the subject will be treated in order. 

Let us take, for example, cyanide of potassium composed of 
the three elements 

C, N, K, 

the union of which will give the final product CNK, and let us see 
under which conditions this product may be formed. 

Three hypotheses are put forth in explaining this formation. 

(1) In the presence of the alkali metal the carbon unites with 
the nitrogen to form cyanogen CN, which, reacting on the alkali 
metal as fast as it is formed, would give the cyanide of this metal 
as end reaction 

(2) The nitrogen unites with the alkali metal to form a nitride, 
which in contact with carbon becomes transformed into cyanide. 

(3) First, there is a union of carbon and potassium, forming a 
carbide, with which nitrogen reacts to produce cyanide. 

The first thing noted in these three hypotheses is that in each 
case the final combination takes place only after an intermediary 
reaction, and that the fixation of nitrogen cannot take place with- 
out this intermediate agent, the nature of which is still undeter- 
mined. The first hypothesis is supported by the following facts: 
When cyanide of potassium is prepared by heating nitrogenous 
animal matter with an alkali carbonate, it is noticed that the for- 
mation of the cyanide takes place only at a temperature in the 
neighborhood of which the alkali carbonate is reduced to a metallic 
state. Therefore the combination C + N is due to the presence of 
the alkali metal. 

Schuetzenberger, among others, puts forth the theory that at 
the temperature of the experiment the carbon tends to become 
separated from the alkali with which it is combined. 

Moreover, if a current of free nitrogen or of ammonia be passed 
over a mixture of alkali carbonate and charcoal heated to bright 
redness, there is formation of cyanide. The same result is obtained 
if nitrogenous matter be heated in the presence of potassium or 
sodium. All these facts would seem, therefore, to prove that the 
presence of an alkali metal is necessary to effect the union of car- 
bon with nitrogen. Another corroboration of these observations 


is the fact that cyanide of sodium is formed with much more diffi- 
culty than cyanide of potassium, a phenomenon which is easily 
explained, since carbonate of sodium is less easily reducible than 
carbonate of potassium. 

The same would be the result if caustic alkalis were used instead 
of carbonates. That cyanogen and oxygen can not coexist in the 
same medium is a known fact; on this account it is necessary first 
to reduce the oxygen compounds in order to permit the formation 
of cyanides. 

A third remark, no less important, to add to the two preceding 
ones, is the following: If a current of nitrogen be passed over car- 
bon, heated to redness, and the product of this operation be brought 
into contact with melted potassium, there will be no formation of 
cyanide. Against these convincing facts the following objection 
is brought: if a current of nitrogen be passed over a mixture of 
charcoal and baryta, heated to a temperature lower than that 
necessary for the reduction of the base, there will be formed a cyanide 
of barium without there having been a previous formation of metallic 

The role played by the metal would therefore seem to be destroyed, 
and the statement just made leads immediately to the discussion 
of the two other hypotheses: formation of a nitride or of a 

Although experiments have not yet clearly proven that the 
formation of cyanides is possible by means of the intermediate 
passage through a nitride, yet this method of formation is ex- 
plicable. Moissan, who prepared nitride of calcium, was enabled, 
however, by bringing this body in contact with charcoal, to obtain 
only very small quantities of cyanide. 

Finally, it is a fact well known that by the action of nitrogen 
on the carbides of the alkaline earths, these become transformed 
into cyanides. This phenomenon may explain the formation of 
barium cyanide mentioned above. 

It is not at all improbable that the same reaction takes place 
with the carbides of the alkali metals, although thus far no real 
experimental data prove it. It still remains to mention Berthelot's 
hypothesis, a theory quite closely related to that of the carbides. 
This investigator, having observed that nitrogen and acetylene unite 


directly under the influence of the electric spark, exploding in a 
mixture of these gases diluted with hydrogen: 

C 2 H 2 + N 2 = 2CNH, 

supposes that the formation of cyanides is preceded by that of the 
acetylide, C 2 K 2 , which, like acetylene, would unite with nitrogen. 

This question is far from being solved. It is only by means 
of thermochemical studies of the various phenomena which con- 
trol these combinations that a clear and exact idea of the conditions 
under which they are formed will be attained. It is to be hoped 
that modern investigators may solve this problem; this would be 
the cause of great progress for the manufacture of cyanide com- 
pounds. The theory of the formation of ferrocyanide is no better 
known. In its preparation, by means of nitrogenous substances 
in the presence of potassium carbonate, a cyanide would be formed 
according to one of the reactions mentioned above, i.e., there would 
be formation of cyanogen, reduction of the carbonate to a metallic 
state, and reaction of .the cyanogen on the metal to form cyanide of 
potassium. The role which iron plays is unknown; all that is known 
is that the ferrocyanide is formed only during lixiviation, yet it is 
necessary that iron be present. The reaction takes place according 
to the following equations : 

2CNK + Fe = (CN) 2 Fe + K 2 , 
4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 , 

2CNK + FeS = (CN) 2 Fe + K 2 S, 
4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 . 

The presence of sulphide of iron is explained as follows : Commer- 
cial potassium carbonate always contains a certain amount of sul- 
phate. This sulphate being subjected to the action of charcoal and 
iron, at a high temperature, generates sulphide of iron according to 
the following equation : 

K 2 S0 4 +4C=K 2 S+4CO, 

K 2 S+Fe+2C+2N-= 


In his treatise on " Medicaments chimiques," Prunier puts forth 
another theory. According to him, nitride of carbon, which is 
produced by calcining animal substances, would react on potas- 
sium carbonate in order to form acetylene. This gas would unite 
with the potassium set free and with the nitrogen of the nitro- 
genous substance, or with nitrogen of the atmosphere, according to 
the following equation: 

C 2 H 2 + K 2 + N 2 = 2CNK + H 2 , 

when the iron would, in its turn, react to form cyanide of iron, 
which, according to the reaction above cited, would become trans- 
formed into ferrocyanide. It is definitely known that the ferro- 
cyanide is not formed during the calcination, for at that tempera- 
ture the ferrocyanide would be decomposed, giving off nitrogen 
and forming bicarbide of iron and potassium cyanide, according 
to Liebig's theory: 

Fe(CN) 6 K 4 = N 2 + 4CNK + C 2 Fe. 

The formation of sulphocyanides, which is readily produced, is 
easily understood because cyanogen remains an unsaturated body, 
as the following formula shows : 


the sulphur, which is bivalent, saturating two of the free atoms, 
while the alkali metal saturates the last. A like reasoning may 
explain the formation of cyanates, the bivalent oxygen of the cya- 
nates replacing the sulphur of the sulphocyanides. 

To sum up the study of the union of carbon with nitrogen is 
interesting from more than one point of view, because of the very 
difficulty which controls its formation and from the numerous bodies; 
to which it may give rise, bodies of which a general study will now 
be made. 




CYANOGEN, C 2 N 2 = 52. 



THE formula of cyanogen is N=C-C=N. It is really a nitride 
of carbon. <y^ H N til= C, , <JL oftA^fc *$ "ruJCtf&i^ 

It was discovered in 1814 by Gay-Lussac, who gave it this name 
because it formed part of the composition of Prussian blue (x v avocr) 
blue, (fevvaw) to generate. 

This discovery exerted considerable influence on the progress 
of chemistry, and on the theories at that time admitted. The 
investigations of Gay-Lussac upon this body which he had jusi 
discovered set forth, in fact, that this compound, because of its 
properties, resembles greatly the halogens, and that in many reac- 
tions it behaves like a simple substance, i.e., it plays the role of an 
element. In fact cyanogen is oftentimes represented by the simple 
formula Cy, instead of CN. 

Cyanogen is a colorless gas, with an odor reminding one of bitter 
almonds. It exerts a decidedly irritating action on the mucous 
membrane, and may in some cases even cause the eyes to water. 

It has a density of 1.8064, when compared with air, or 25.533 
(H = l). One liter weighs 2.235 grams. 

One volume of water at 20 C. dissolves 4J times its volume of gas, 
whereas alcohol dissolves 25 times its volume. 

It becomes a liquid at 20.7 C. under ordinary pressure, and at 

? 10 


15 C. under a pressure of 4 to 5 atmospheres. This liquid is trans- 
parent and mobile, with a density of 0.866. 

The evaporation of this liquid in open air causes such a lower- 
ing of temperature that the portion not evaporated becomes solid. 
Solid cyanogen melts at -34 C. 

Cyanogen gas burns in air with a purple flame, producing nitro- 
gen and carbonic acid: 

= C0 2 +N. 

It is readily decomposed by heat. Its formation is endothermic, 
and that is the reason why it cannot be obtained by the direct union 
of carbon and nitrogen. 7 <^//3- 

The electric spark breaks it up into its elements; a mixture of 
1 vol. of cyanogen and 2 vols. of oxygen explodes under the influ- 
ence of the electric spark into 1 vol. of nitrogen and 2 vols. of car- 
bonic acid. 

An aqueous solution of cyanogen becomes quickly altered in the 
light; a black flocculent precipitate, called azulmic acid, Cy n (H 2 0) n 
or C4H4N402, separates out, caused by the union of 4 equivalents 
of water and 4 equivalents of cyanogen, while in the solution there 
remain carbonic anhydride, hydrocyanic acid, ammonia, urea, and 
ammonium oxalate (Woehler). 

The same result is observed in an alcoholic or ether solution. 
The presence of an acid suffices to prevent these transformations. 
The same substances are produced in an ammoniacal solution as in 
an aqueous solution. 

Cyanogen does not unite directly with hydrogen. If a mix- 
ture of equal volumes of cyanogen and hydrogen be passed in a 
tube heated to 500 C., only traces of hydrocyanic acid are obtained. 

On the other hand, cyanogen unites with nascent hydrogen, pro- 
ducing ethylene diamine; finally, if sealed tubes heated to 500 C. 
are employed, the union of the two gases is complete. 

Cyanogen does not unite directly with chlorine, even in the 
light; but if the two gases are moist, an oily liquid and a solid 
aromatic substance are formed. 

On the other hand, cyanogen is decomposed by hypochlorous 
anhydride, and by hypochlorous acid, with formation of carbonic 
acid, chlorine, nitrogen, and gaseous cyanogen chloride. 


It does not unite directly with sulphur, but when cyanogen and 
hydrogen sulphide are brought together in a moist state two crys- 
tallizable compounds are formed, a monosulphydrate and a bisul- 
phydrate of cyanogen, corresponding respectively to the formulas 
C2N2.SH 2 and C2N 2 .(H 2 S) 2 . The mono- or the bisulphydrate is 
obtained according as an excess of cyanogen or of hydrogen sul- 
phide is used. 

In a heated state, cyanogen absorbs potassium, with formation 
of potassium cyanide. An aqueous solution of potash absorbs the 
gas energetically, with formation of azulmate of cyanide, cyanate 
and oxalate of potassium. 

It combines directly with zinc, with cadmium at 300 C., and 
with lead at 500 C. Heated to redness with iron, the latter absorbs 
the carbon, setting the nitrogen free, the metal becoming brittle. 
With the other metals it unites only indirectly. 

Some organic bases may unite with it, e.g., aniline, toluidine, 
codeine, producing cyaniline, cyanotoluidine, cyanocodeine, respect- 
ively, bodies which may be decomposed by an alkali with formation 
of oxalic acid or its derivatives. Cuprous chloride absorbs it. It is 
decomposed by manganic sulphate, which reduces it to carbonic 
acid and nitrogen. Mercurous oxide absorbs it slowly. 

Potassium carbonate, heated to redness, absorbs cyanogen, with 
production of cyanide and cyanate of potassium. 

Properly stated, cyanogen does not exist free. Yet, in certain 
cases it is found in small quantities, as, for example, in the gases 
of the blast-furnace, where one finds as much as 1.34%. It is also 
formed when a mixture of illuminating-gas and ammonia is burned 
in a Bunsen burner. 

It is formed, indirectly, in the following reactions: 

(1) When nitrogenous animal substances are burned in pres- 
ence of an alkali carbonate, particularly potassium carbonate. 

(2) When nitrogenous animal substances are burned in the pres- 
ence of potassium. 

(3) When nitrogen acts on a mixture of charcoal and potash. 

(4) When ammonia acts on charcoal, heated to redness. 

In these reactions, however, it is always combined; and it is 
as a cyanide of potassium, sodium, or ammonium that it may be 
extracted. These methods of formation constitute the base of the 


process of the manufacture of alkali cyanides, of which more in a 
later chapter. 

Cyanogen may be prepared by various methods. 

(1) By heating dry mercuric cyanide to dull redness in a retort: 

Hg(CN) 2 = (CN) 2 + Hg (Gay-Lussac) . 

(2) By heating in a retort an intimate mixture of 2 parts potas- 
sium ferrocyanide and 3 parts of mercuric chloride (Kemp). 

(3) By the dry distillation of ammonium oxalate or of oxamide: 

C 2 4 (NH 4 ) 2 = 4H 2 + (CN) 2 . 

(4) By heating glycerine and ammonium oxalate at 200 C. 

(5) By heating, on an oil-bath at 160-170 C., a dry mixture 
of zinc cyanide and cupric chloride, there is formed cupric cyanide 
which, under the influence of heat, loses one half of its cyanogen, 
and becomes transformed into cuprous cyanide and cyanogen. 

It is likewise produced by heating, under the same conditions, 
a solution of copper sulphate into which a concentrated solution 
of potassium cyanide is gradually poured (Varet) 

Finally, cyanogen is formed with an absorption of heat 38 
calories, when carbon in the state of the diamond is used: 

C(diamond) + N = CN - 38 cal. 

This is a polymeric modification or an isomer of cyanogen, which 
is always produced in the preparation of cyanogen by the decom- 
position of the cyanides of mercury or of silver by heat, the amount 
of paracyanogen increasing in proportion as the temperature is low. 

It is also obtained by heating cyanogen in a closed vessel; but, 
on the other hand, when paracyanogen is likewise heated out of 
contact with air it is decomposed into cyanogen. However, when 
the vapor of cyanogen exerts a definite pressure on the paracyanogen 
remaining, the production of the former ceases. This tension of 
transformation varies proportionally with the temperature, but it 
is constant for a given temperature. 



Troost and Hautefeuille determined the conversion tension of 


Tension of 


Tension of 


54 mm. 


275 mm. 


125 " 


318 " 


129 " 


868 " 


157 " 


1310 " 

This is therefore a phenomenon quite analogous to that of the 
allotropic transformation of white phosphorus into red phosphorus. 

Paracyanogen is a brownish-black powder, insoluble in water, 
soluble in concentrated sulphuric acid. It becomes converted into 
cyanogen on heating in a current of inert gas, such as carbonic 
acid or nitrogen. 


f C = 44.44 

100CNH= |N = 51.85 
lH= 3.71 


Hydrocyanic acid or nitride of formic acid has the formula 
CNH. It is also called prussic acid. It was discovered by Scheele 
in 1782, but Gay-Lussac was the first to obtain it in a pure state, 
in 1811, and to establish its composition. It was known to Egyptian 
priests, who used it in the killing of traitors. 

It occurs in certain plants; in the leaves of the laurel-cherry 
and the laurel-leaf willow, in the leaves and blossoms of the peach, 
and in bitter almonds. The kernels of most of the stone-fruits 
contain some. The root of Jatropha Mannihot also contains it, 
from which it may be obtained by distillation with water. 

It is produced by the breaking up of the amygdalin, a neutral 
substance found in various plants, by the action of water. 

It is the hydrocyanic acid which gives to liquors prepared with 
almonds their characteristic odor and flavor. 

Hydrocyanic acid is sometimes obtained in the distillation of 
nitrogenous products, and in the oxidation of certain organic sub- 
stances with nitric acid. 


Formate of ammonium heated to 200 C. loses water and forms 
hydrocyanic acid: 

CH0 2 .NH 4 -2H 2 = 

The action of the electric spark on a mixture of acetylene and nitro- 
gen gives hydrogen cyanide: 

C 2 H 2 +N 2 =2CNH (Berthelot). 

When an electric furnace is started, a perceptible odor of laurel- 
cherry, due to hydrocyanic acid, is noticed. This is produced by 
the union of atmospheric nitrogen with acetylene, which latter is 
formed by the union of the carbon of the electrodes with the hydrogen 
due to the decomposition of water- vapor by the voltaic arc. Hydro- 
gen cyanide is also produced by the action "of chloroform on 
ammonia : 

= 3HC1+CNH. 

It is likewise produc d in appreciable quantities in the combustion 
of a mixture of air and nitrogen dioxide in an inverted Bunsen 
burner; likewise in tobacco-smoke; and by the passage of an electric 
discharge in 9% aniline; and in the electric arc 

To obtain it pure, mercuric cyanide is, as a rule, decomposed by 
hydrochloric acid (Gay-Lussac) when there is formed hydrocyanic 
acid and corrosive sublimate; but, on account of the affinity of this 
salt for hydrocyanic acid, the yield is rather small This can be 
remedied by the addition of ammonium chloride, which unites with 
the sublimate (Bussy & Buignet): 

(CH) 2 Hg + 2HC1 = HgCl 2 + 2CNH. 

The best procedure consists in treating potassium ferrocyanide 
with sulphuric acid (15 parts ferrocyanide, 7 sulphuric acid, 9 water;. 
The gas first passes over calcium chloride, and is then collected in a 
cylinder surrounded by a cooling mixture. In this way the anhy- 
drous acid is obtained. To obtain the aqueous acid, it is only neces- 
sary to distil the mixture: 

2[Fe (ON) 6 K 4 ] + 3H 2 S0 4 - 3K 2 SO 4 + 6CNH + Fe(CN) 6 K 2 Fe. 
Several other processes have been brought out: 


Clarke's process, which consists in adding 4 parts of potassium 
cyanide to a solution of 9 parts of tartaric acid in 60 parts of water. 
In this case cream of tartar separates out, leaving a supernatant 
liquid of hydrocyanic acid. 

Everitt's process is based on the decomposition of silver cyanide 
by hydrochloric acid: 

CNAg + HC1 - CNH + AgCl. 

Thompson's process is based on the decomposition of lead 
cyanide by sulphuric acid: 

(CN) 2 Pb + H 2 S0 4 = 2CNH + PbS0 4 . 

Vauquelin's process consists in passing a current of hydrogen 
sulphide over very dry mercuric cyanide. 

Kuhlmann's process is likewise of interest. Dry ammonia gas is 
passed through a glass tube filled with pieces of charcoal, and heated 
to redness. The gas formed is conducted through dilute sulphuric 
acid at 50 C., and then into a cooled receiver. Ammonium cyanide 
is formed, which in contact with sulphuric acid forms ammonium 
sulphate and hydrocyanic acid: 

= CN-NH 4 +H 2 

2(CN NH 4 ) +H 2 S0 4 -- 2CNH + (NH 4 ) 2 S0 4 . 

The anhydrous acid is a colorless liquid of specific gravity 0.7058 
at 7C., and 0.6969 at 18 C. It becomes a solid at -15C., boils 
at 26.5 C. Its vapor density is 0.9467. 

Its odor is characteristic of bitter almonds. It is soluble, or 
rather miscible with water and alcohol in all proportions. The 
density of its aqueous solutions decreases in proportion as the 
amount of acid in solution increases. Thus a 1% solution has a 
specific gravity of 0.9988, while a 16% solution has a specific gravity 
of only 0.9570. Its aqueous solution is a union. In fact, if equal 
parts of the two bodies be mixed, a loss of 25% in vapor-tension is 
produced. When dry, it burns in air with a white flame tinged with 
violet, with formation of water, carbonic acid, and nitrogen: 

2CNH +50 =H 2 +2C0 2 +N 2 . 


It decomposes rapidly in the light, yielding ammonia and a brown 

The presence of a small quantity of mineral acid renders it more 
stable. A trace of ammonia decomposes it very rapidly. Concen- 
trated mineral acids transform it very quickly by fixing 2 molecules 
of water into formic acid and ammonia. Dilute alkalis, in the cold, 
produce, with it, the corresponding cyanides: 

KOH + CNH = CNK = H 2 ; 

but when boiled, or with concentrated alkalis, there is a formation 
of alkali formate and ammonia: 

CNH + KOH + H 2 = NH 3 + HCOOK 

It is likewise decomposed by chlorine and bromine, yielding 
hydrochloric acid, hydrobromic acid, and crystalline compounds, 
such as hydrochloride and hydrobromide of cyanogen. 

In the presence of slightly warmed potassium it yields potassium 

Nascent hydrogen reduces it to methylamine: 

CNH + H 4 = CH 3 NH 2 (Mendius). 

Heat breaks it up into hydrogen, cyanogen, nitrogen, and carbon. 
The electric spark decomposes it nearly completely only when it 
is mixed with hydrogen, or when it is in an aqueous solution. 

Manganese dioxide absorbs gaseo s hydrocyanic acid entirely 
when mixed with hydrogen. It is a weak acid which does not de- 
compose carbonates. It is formed by the union of equal volumes 
of hydrogen and cyanogen without condensation. 

Action on the System. Prussic acid is the most violent and rapid 
poison known. A dose of 5 centigrams suffices to kill a man. One 
drop of this acid placed on the tongue of a dog renders him instantly 
unconscious. Scheele, the discoverer of hydrocyanic acid, himself 
died, poisoned by it. Scharinger, a chemist of Vienna, died in two 
hours, the result of letting two drops of this acid fall on his arm. 

Its vapors are likewise extremely poisonous. Their respiration 
causes violent headaches, nausea, pains, and oppression in the chest. 

In gold-mines where the cyanide process is in use, workmen 


whose duty it is to clean the vats are affected with general weak- 
ness, headaches, dizziness, and nausea. Often a kind of eruption, 
especially on the arms, breaks out in them. These eruptions may 
be readily overcome by internal and external application of potassium 

Prussic acid seems to affect the circulatory rather than the nervous 
system; it destroys muscular sensibility, and death results through 
suspension of the heart's action. 

Quite often the victim is seized, before death, by violent attacks 
of tetanus. 

Properly speaking, there is no antidote for prussic acid. Inhala- 
tion of chlorine and of ammonia have been advised, but ammonium 
cyanide and cyanogen chloride are themselves just as poisonous. 

If these bodies have sometimes produced favorable effects, these 
must rather be attributed to an excitation of the nervous system. 
Likewise, internal application of essence of turpentine (30 grams 
in emulsion by spoonful) have been advised. The affusion of 
cold water on the spinal column and on the base of the skull are 

Robert and Krohl have quite recently p aised the use of hydrogen 
peroxide as an antidote for prussic acid A 30% solution is used 
internally, and a 3% solution for subcutaneous injections. The 
following reaction takes place: the hydrocyanic acid, reacting with 
hydrogen peroxide, is changed into oxamide, which is non-poisonous : 

This method has been quite successfully used in the English gold- 
mines for the past four years, and in many cases subcutaneous 
injection suffices. Dr. Autal of the Austria-Hungary Medical 
Association (June 2, 1894) recommended the use of cobalt nitrate. 
This salt forms with potassium cyanide an insoluble and harmless 


By its union with metals, hydrocyanic acid forms cyanides or 
cyanhydrates, salts which are analogous to chlorides, bromides, and 


Cyanides may be divided into two classes, simple and double 

The simple cyanides, especially the alkali cyanides, are formed 
in many reactions : 

(1) By the action of cyanogen or of gaseous hydrocyanic acid 
on the slightly heated metal. 

(2) By heating carbonates or hydrates of alkalis in a current 
of cyanogen. 

(3) By double decomposition of hydrocyanic acid and metallic 

(4) By the action of a current of nitrogen upon a mixture of 
charcoal and hydrate or carbonate of an alkali. 

(5) By the ignition of nitrogenous organic substances in the 
presence of alkalis, hydrates or carbonates, nitrites or nitrates. 

(6) By the action of ammonia-gas upon charcoal, heated to 
redness, or of carbon monoxide upon ammonia, likewise at a red 

2NH 3 -fC = CN-NH 4 +2H. 

As to the other cyanides, they are generally obtained by the 
double decomposition between a metallic salt and an alkali cyanide. 

Properties. The cyanides of the alkali metals and of the alkaline 
earth metals are soluble in water and in alcohol, with formation 
of a strong alkaline solution; the cyanides of the other metals are 
insoluble, excepting mercuric cyanide. The cyanides of the 
alkalis and of the alkaline earths are not decomposed by heat, in 
the absence of air; but in contact with oxygen they are transformed 
into cyanates: 

CNK + 0=CNOK. 

The other cyanides are decomposed by heat. In the presence of 
water and of heat they are all decomposed. Cyanides of the heavy 
metals give carbon monoxide, carbon dioxide, ammonia, carbon, 
and the metal; the other cyanides give formates and ammonia. 

Cyanides have reducing properties. They reduce metallic oxides, 
being themselves transformed into cyanates. 

Mineral acids, e.g., hydrochloric, sulphuric, decompose them, 


setting free hydrocyanic acid. Nitric acid decomposes them into 
nitrates, carbonic acid, and nitrogen: 

CNK + 2HN0 3 = KN0 3 + C0 2 + 2N + H 2 0. 

When the oxides of the heavy metals are digested with a solu- 
tion of an alkali cyanide, a large part of them is converted into 
cyanides, whereas the alkali metal becomes hydrated: 

2CNK + HgO + H 2 = Hg(CN) 2 + 2KOH. 

They unite with the metallic chlorides, bromides, iodides, nitrates, 
and chromates. 


= 18.46 

100CNK= -I N = 21.54 
= 60.00 


Potassium cyanide, KCN = 65, is a white substance having an 
acrid and slightly bitter taste, leaving an after-taste of hydro- 
cyanic acid. It has a strong, penetrating odor which is character- 
istic. It crystallizes in anhydrous octohedrons, which are easily 
fusible and deliquescent. It has an alkaline reaction. It is vola- 
tile at a white-red heat without decomposition. It is easily soluble 
in cold, more so in boiling water (100 parts boiling water dissolve 
122 parts), slightly soluble in strong alcohol. Its solubility in alco- 
hol increases in proportion as the alcohol is diluted. 

When in solution, or even in a moist state, it is acted upon by 
carbonic acid, with formations of hydrocyanic acid and potas- 
sium carbonate: 

2CNK + C0 2 + H 2 = K 2 C0 3 + 2CNH. 

- This reaction is of great importance from the manufacturing 
standpoint; for it shows how little stable that body is, and the. 
means necessary to be taken to prevent its decomposition and to 
keep it intact. 

When its aqueous solution is heated to boiling out of contact 
with air, it breaks up into potassium formate and ammonia. In 
this way it may be completely decomposed. 


Dry carbonic acid like dry air does not react on dry potassium 
cyanide. It is easily oxidized, which means that it is an energetic 
reducing agent. When burned in air, or with manganese dioxide, 
or with iron oxide, it is converted into a cyanate. This property 
was the cause of its being used in the reduction and separation of 
certain metallic oxides; it has the advantage over other reducing 
agents of not carburetting the metal. This reaction takes place 
generally at temperatures only slightly raised. It is likewise 
oxidized by chloride of lime, which converts it into cyanate of lime. 
When its aqueous solution is treated by an electric current it is 
converted into cyanate. 

It also works as a reducing agent in a wet way. 

When fused with sulphur it is changed into sulphocyanide: 

CNK + S = CNKS. 

This same result is obtained when it is fused with sulphide of 
tin or of antimony. 

Its aqueous solution dissolves several metallic oxides, and even 
metals; e.g., copper, zinc, nickel, iron. Mercury, platinum, tin 
are not dissolved by it; cadmium, silver, gold are dissolved by 
it, but only in contact with air. This last property is of the 
greatest importance, for to it is due the development of the 
manufacture of the alkali cyanides. Likewise, chloride of silver, 
selenium, tellurium, and iodine are dissolved by it. In the case 
of iodine there is formed cyanogen iodide, or a double iodide of 
cyanogen and potassium. 

Heated with nitrate or chlorate of potassium a violent explosion 
takes place. When potassium sulphate is fused with potassium 
cyanide, the latter becomes converted into cyanate of potassium, 
and there is also formed potassium sulphide. When hydrogen 
sulphide is passed through a concentrated aqueous solution of potas- 
sium cyanide, an intense red coloration results, with formation of 
yellow needles of chryseane,. CJIsH^. 

When sulphurous acid is passed through a cooled 40% solution 
of potassium cyanide hydrocyanic acid is set free, the solution 
becomes brown, and in a few days there are formed crystals of cyano- 
sulphite of potassium, S0 2 CNK + H 2 0, a solution which possesses 


the property of reducing salts of gold and silver. When this solu- 
tion is treated with acids there is formed acid - cyanosulphite of 
potassium, which is only slightly soluble and decomposable by heat. 

Potassium cyanide is decomposed by permanganate of potash. 

The most remarkable and interesting property of potassium 
cyanide is that of dissolving gold in the presence of the oxygen 
and moisture of the atmosphere, since this property is the cause 
of its extensive use in industry. This solution takes place according 
to the following reactions: 

4CNK + Au 2 + + H 2 = 2([CN] 2 KAu) + 2KOH. 

When treated with zinc, this new compound yields metallic 
gold, with formation of a double cyanide of zinc and potassium: 

2([CN] 2 KAu) + Zn = 2(CNK,[CN] 2 Zn) +Au 2 . 

In reality the reaction takes place in another way; at least 
it is explained in the following manner: Zinc causes the formation 
of a voltaic couple, and in general, where the solution contains 
potassium-gold-cyanide and cyanide of potassium in excess, and 
zinc, the following reactions fake place: 

4CNK + Zn + 2H 2 = 2(CNK,[CN] 2 Zn) + 2KOH + H 2; 

2[(CN) 2 KAu] + H 2 = 2CNH + 2CNK + Au 2 , 

CNH + KOH = CNK + H 2 0. 

Not its least interesting property is that of dissolving certain metallic 
sulphides, such as those of copper, silver, gold, zinc, iron, which 
may be used in metallurgy. 

Finally, it possesses extremely toxic properties. Two centi- 
grams of this salt suffice to cause the death of a man. 

In case of poisoning by this compound, the following treatment 
is recommended: Cause the patient to breathe chlorinated water, 
liquor of Labarraque, or ammonia; administer doses of essence of 
turpentine (30 grams in emulsion) or multiple antidote of Jeannel; 
affusions of cold water on the head, anodynes, and tonics. 



f C =24.49 

100CNNa = i N =28.57 
lNa = 46.94 


It corresponds to the formula CNNa = 49. 

It is formed in the same way as is potassium cyanide. Its' prop- 
erties are almost identical. It is rather difficult to obtain it in 
crystalline form, for its aqueous solution evaporates in a mass. 
The only important difference between sodium and potassium 
cyanide is that the former contains more cyanogen, which is to 
its advantage For example, the atomic weight of CNNa is 49, 
of which 26 is cyanogen, i.e., 53%, while the atomic weight of CNK 
is 65, of which 26 is cyanogen, or only 40%. 

On account of the progress of electrochemistry in preparing 
metallic sodium in large quantities and at a moderate price, sodium 
cyanide is daily becoming of greater importance. 

Yet the use of potassium cyanide is preferred in industry, because 
it is not deliquescent and therefore may be more easily transported. 
At present a double cyanide of sodium and potassium is being pre- 
pared (CN) 2 NaK, which makes possible the use of a larger quantity 
of free cyanogen under a less weight. 


r C = 27.27 
100CN-NH,= | N = 63.63 

LH= 9.10 


Ammonium cyanide or cyanhydrate of ammonia, CN-NH4 = 44, 
is a solid, colorless product crystallizing in cubes or quadrangular 
prisms. It has an alkaline reaction, and an odor reminding one of 
both hydrocyanic acid and ammonia. It is readily soluble in water 
and alcohol, and quite unstable in air, especially when heated. At 
36 C. it undergoes partial volatilization and is converted into azul- 
mic acid. Its vapors are inflammable. It is very poisonous. 

It may be prepared as follows: 

(1) By the action of ammonia on charcoal heated to redness 


if the product of the reaction be collected in a cylinder surrounded 
.by a freezing mixture: 

C+2NH 3 = CN-NH 4 +H 2 . 

(2) By the double decomposition of ammonium chloride and 
the cyanides of potassium or of mercury, or ferrocyanide of potas- 
sium. Ammonium cyanide exists already formed, as will be seen 
later, in illuminating-gas 


rC =26.09 

100Ca(CN) 2 = \ N =30.43 
LCa = 43.48 


It occurs as anhydrous crystalline cubes, soluble in water. Its solu- 
tion is decomposed by heat and carbonic acid. It is prepared by 
the action of hydrocyanic acid on a solution of lime or on milk of 

BARIUM CYANIDE, Ba(CN) 2 = 189. 

rC =12.70 

100Ba(CN) 2 = \ N =14.81 
Ba = 72.49 


It is obtained by heating ferrocyanide of barium in a closed 
tube (Berzelius), or by saturating baryta water with hydrocyanic 
acid (Ittner), or, still more easily, by the action of nitrogen upon a 
mixture of charcoal and of baryta heated to redness (Margueritte 
and Sourdeval). This last reaction has been applied industrially. 

It is soluble in water and in alcohol and is decomposed by heat. 
For a long time its use has been praised in metallurgy for the cemen- 
tation of steel. 


This is not yet known. 

CYANIDE OF ZINC, Zn(CN) 2 = 117. 

rC =20.51 
100Zn(CN) 2 = N =23.93 



It is a white substance, insoluble in water and in alcohol, soluble 
in the alkali cyanides with formation of double cyanides. It is 
prepared either by the double decomposition of zinc sulphate and 
potassium or ammonium cyanide, or by the action of hydrocyanic 
acid on the acetate or hydrate of zinc. 


The simple cyanides of iron are little known, because of the^ 
extreme ease with which they are transformed into the complete- 

Two of them are known from which a whole series of double salts,' 
are derived: they are ferrous cyanide, Fe(CN) 2 , and ferric cyanide,. 
Fe 2 (CN) 6 . The ferrocyanides correspond to the former, while the? 
ferricyanides are derived from the latter. 


Chromous cyanide, Cr(CN)2, is white It is obtained by pre- 
cipitating a solution of chromous chloride with potassium cyanide. 
It is soluble in an excess of potassium cyanide and is easily changed 
in the air, giving oxide of chromium and chromic cyanide. 
Chromic cyanide, Cr 2 (CN) 6 , is more stable; it is obtained by pre- 
cipitating at the boiling-point a solution of chromic chloride with 
an excess of potassium cyanide. These two cyanides form respect- 
ively chromous and chromic cyanides, analogous to ferrous and 
ferric cyanides. 


Only the double cyanides are known, Manganous and manganic 
cyanides, which will be studied later. 

This is unknown in a free state. 

CYANIDE OF LEAD, Pb(CN) 2 =258. 

fC = 9.30 

100Pb(CN) 3 = JN =10.85 
LPb = 79.85 



It is but imperfectly known. When prepared by the action of 
ammonium cyanide and lead acetate it is yellow, while, when it 
is obtained by the addition of hydrocyanic acid to an ammoniacal 
solution of lead subacetate it is white. Kugles gives it the formula 
Pb(CN)OH, while Erlenmeyer designates it by Pb(CN) 2 2PbO. 

CYANIDE OF COPPER, Cu 2 (CN) 2 = 178. 

fC =13.49 

100Cu 2 (CN) 2 = | N =15.73 
u = 70.78 


Cuprous cyanide, Cu2(CN)2, only is stable. It is a white powder 
which is precipitated by the action of hydrocyanic acid on an hydro- 
chloric acid solution of cuprous chloride 


fC = 9.52 

100Hg(CN) 2 = |N =11.11 
lHg = 79.37 


Mercuric cyanide, Hg(CN)2, only ,is known. It crystallizes in 
opaque, colorless prisms soluble in water, insoluble in alcohol. It is 
prepared by dissolving mercuric oxide in hydrocyanic acid, or by 
boiling one part of potassium ferrocyanide, two parts of mercuric 
sulphate, with eight parts of water. It is decomposable by heat, con- 
centrated acids, bromine, iodine, and chlorine (under the influence 
of solar rays). It is very poisonous. 


fC = 8.96 

100Ag(CN)= \ N =10.44 
[Ag = 80.60 


It is a white substance, closely resembling silver chloride. It is 
obtained by precipitating a solution of silver nitrate with potassium 
cyanide. It is soluble in ammonia, and in hot, concentrated nitric 
acid, and in the alkali cyanides and chlorides. 



rC =21.63 

100Co(CN) 2 = \ N =25.22 
I Co = 53.15 


Cobaltous cyanide, Co(CN)2, is a flesh-colored precipitate, ob- 
tained by precipitation of a cobalt salt with potassium cyanide. 
Oxygen of the atmosphere changes it rapidly. 


rC =21.63 
100Ni(CN) a = N =25.22 


It is an apple-green substance obtained by precipitating a salt 
of nickel with potassium cyanide, or by the action of hydrocyanic 
acid on nickel acetate. It crystallizes with 3 molecules of water. 


C = 5.41 

lOOAu(CN) = -j N = 6.31 
Au = 88.28 


Aurous cyanide, Au(CN), is a beautiful pale-yellow crystalline 
powder, very stable, insoluble in water, alcohol, and acids: It is 
odorless and tasteless. Heat decomposes it into cyanogen and gold. 
Boiling potash decomposes it slowly into potassium gold cyanide 
and metallic gold, soluble in ammonium sulphydrate, ammonia, 
and sodium hyposulphite. 


rC = 9.64 

100Pt(CN) 2 = \ N =11.24 
I Pt- 79,12 


Platinous cyanide, Pt(CN)2, is greenish yellow, insoluble in- 


water, acids ; and alkalis. It burns in air, leaving a residue of me- 
tallic platinum. 


Most of the cyanides are capable of combining together to form 
double cyanides. Often they are produced by dissolving a simple 
insoluble cyanide in a soluble alkali cyanide. 

There are two classes of double cyanides, the stable and the 

The unstable double cyanides are decomposed by dilute acids, 
when the insoluble cyanide is precipitated and hydrocyanic acid 
set free; the gas set free results from the action of the acid used 
on the existing alkali cyanide. 

The stable cyanides, on the other hand, resist the action of dilute 
acids. In this case there is only a substitution of the hydrogen for 
the potassium (potassium cyanide is the one usually employed) , 
and there is formed a double cyanide of hydrogen and heavy metal. 

Salt solutions of nearly all metals, acting on double cyanides, 
produce the phenomenon of double decomposition. 

On account of these differences, the unstable cyanides are generally 
considered as true double cyanides, i.e., formed by two simple 
cyanides, while, on the other hand, the stable cyanides are the result 
of the union of an alkali metal with the radical formed when 
cyanogen combines with the heavy metal. 

This hypothesis seems to be verified from the following: In the 
stable double cyanides the heavy metal (by heavy metal is meant 
all metals except alkali arid alkaline earth metals) cannot be re- 
leased by its ordinary reactions; moreover, hydrogen may be sub- 
stituted for the alkali metal; besides, they are neutral and non- 
poisonous. On the con rary, in the unstable double cyanides hydrogen 
cannot be substituted for the alkali metal, and the heavy metal and 
even the cyanogen are more easily recognized by their reagents. 

The necessity of expressing the special stability of one of the two 
classes of these compounds has caused them to be designated by 
special names: ferro-, ferri-, cobalto-, chromo-, chromi-, platino- 
cyanide, etc. Among the double cyanides, only the most important 
will be studied, and first among these the f errocyanides and the f erri- 



Ferrocyanide of potassium has the following composition: 

(Fe =15.22 

100Fe(CN) 6 K 4 = j CN = 42.39 
IK =42.39 


This salt, which is also called ferrocyanhydrate, cyanoferride > 
double cyanide of iron and of potassium, hydroferrocyanate, yellow 
prussiate of potash, corresponds to the formula Fe(CN) 6 K 4 . It 
crystallizes with 3 molecules of water in voluminous monoclinic 
prisms. It has a citron-yellow color, is flexible, vitreous, and pos- 
sesses a salty, bitter taste. Its density is 1.833. At 60 C. it loses. 
its water of crystallization, which, however, does not completely 
disappear except at 100 C. It is then converted into a white 
powder. It is soluble in water, which dissolves two parts in cold 
and four in hot water. Its aqueous solution saturated at 15 C. 
has a density of 1.444. 

In absence of air it fuses just below red heat with the produc- 
tion of nitrogen, potassium cyanide, and iron carbide: 

Fe(CN) 6 K 4 = FeC 2 + 4CNK + N 2 . 

In contact with air, potassium cyanate and peroxide of iron 
are formed. 

When burned in the presence of an alkali it is entirely con- 
verted into cyanide of potassium: 

Fe(CN) 6 K 4 + K 2 C0 3 = 6CNK + FeO + C0 2 . 

These various reactions are of great importance and are utilized,, 
as will be seen more in detail later, in the industrial manufacture of 

Oxygen exerts no action on ferrocyanide of potassium, but ozone, 
the electric current, chlorine, bromine, dilute nitric acid, peroxide of 
lead, manganese dioxide, permanganate of potash, all transform 
it either wholly or in part into potassium ferricyanide. These 
various reactions may be expressed thus: 


With chlorine, 

2[Fe(CN) 6 K 4 ] + C1 2 = Fe 2 (CN) 12 K 6 + 2KC1. 
With the electric current, 

2[Fe(CN) 6 K 4 ] + 2H 2 = 2KOH + H 2 + Fe 2 (CN) i 2 K 6 . 

These two reactions are used industrially in the preparation 
of ferricyanide of potassium. 

Sulphur converts it into sulphocyanate. When ferrocyanide of 
potassium is treated with dilute sulphuric acid there is formed 
hydroferrocyanic acid: 

[Fe(CN) 6 K 4 ] +2H 2 S0 4 = 2K 2 S0 4 +Fe(CN) 6 H 4 . 
To hydroferrocyanic acid Friedel attributes the following formula: 




I | 


With concentrated sulphuric acid there is formed carbon mon- 
oxide, sulphates of iron, potassium, and ammonium: 

Pe(CN) 6 K 4 + 6H 2 S0 4 + 6H 2 = 6CO + FeS0 4 + 2K 2 S0 4 + 3(NH 4 ) 2 S0 4 . 

This reaction is explained as follows : The sulphuric acid is com- 
bined with iron and potassium sulphates; hydrocyanic acid in pres- 
ence of moisture has yielded ammonium formate, which, acted 
upon by sulphuric acid, is converted into ammonia and carbon 

The ammonia thus formed unites with sulphuric acid to form 
sulphate of ammonia, while the carbon monoxide is set free. 

The other alkali ferrocyanides of sodium and ammonium have 
similar properties. They are soluble in water, insoluble or only 
slightly soluble in alcohol. 


Ferrocyanide of sodium, Fe(CN) 6 Na 4 -f 12H 2 0, has been pro- 
posed as a substitute for ferrocyanide of potassium, but so far it 
has no^ been possible to use it industrially on account of the enor- 
mous quantity of water of crystallization which it contains and 
which renders its transportation much more expensive. 

The alkaline-earth ferrocyanides are white and insoluble. 

The other metallic ferrocyanides have various colors, which are 
frequently used in chemical analyses. 

The most interesting are those of barium, which are white and 
very soluble ; the cuprous salt, which is red, and the cupric, which is 
white; the nickel, which is greenish white, and the lead, which is 

Ferrocyanide of iron is, among these latter, very interesting; the 
ferriferrocyanide is more generally known under the name Prussian 

[Fe(CN) 6 ] 3 Fe 4 + 18H 2 0. 

This Prussian blue is formed by the action of a ferric salt on 
potassium ferrocyanide : 

3Fe(CN) 6 K 4 +2Fe 2 Cl 6 = (Fe(CN) 6 ) 3 Fe 4 + 12KC1. 

It is a dark-blue powder, odorless and insipid. Its fracture has a 
copper-like lustre. It loses its water of crystallization completely 
only when decomposed. 

It is insoluble in water, alcohol, ether, and weak acids. It is 
soluble in ammonium tartrate and in oxalic acid, giving a violet 
solution in the former case and a blue solution in the latter. 

When burned it yields carbonic acid, and water, and carbonate 
and cyanhydrate of ammonia. 

When treated with concentrated sulphuric acid it is converted 
into a white pitchy mass, which on the addition of water is recon- 
verted into Prussian blue. It is but slowly affected by hydro- 
chloric acid. Potassium hydroxide converts it into ferric hydrate 
and potassium ferrocyanide. This reaction is utilized in the manu- 
facture of potassium ferrocyanide extracted from the purifying 
materials of illuminating-gas. 

The alkali carbonates act in the same way, but less easily. 


Soluble Prussian blue is the name given to the compound formed 
by the union of ordinary Prussian blue with f errocyanide of potassium* 


Beside the ferrocyanides is placed another class of double cyan- 
ides which is derived from them the ferricyanides. Ferricyanides 
may be considered as double ferrocyanides minus 2 atoms of metal: 

2Fe(CN) 6 K 4 -K 2 = Fe 2 (CN) 12 K 6 . 

The tetratomic ferrocyanogen radical, Fe(CN) 6 , uniting with 
itself by exchanging two valences, is transformed into the hexatomic 
radical Fe2(CN)i2- Various authors consider the ferricyanides as 
double cyanides of ferric iron with another metal; others, on the 
other hand, think that they result from the union of a metal with 
the radical Fe 2 (CN)i 2 . 

The following ferricyanides are known: Potassium, red; silver, 
orange; barium and potassium, black; calcium, gold color; cobalt, 
red; copper, yellow; nickel, greenish yellow. 

The ferricyanides of the alkalis and of the alkaline earths only 
are soluble; the others are, as a rule, insoluble. 

The most interesting is ferricyanide of potassium, also called 
cyaniferride, red prussiate of potash. The discovery of this salt 
was made by Gmelin. Its percentage composition is as follows: 

fFe =17.02 

100Fe 2 (CN) 12 K a = | CN = 47.42 
[K =35.56 


It occurs as red rhombic anhydrous prisms, having a density 
of 1.800 to 1.845 according to different investigators. It has a 
salty taste, is soluble in water, especially so in hot water. At 4.4 C. 
one part of the salt is soluble in 3.03 parts water, yielding a solution 
whose sp. gr. is 1.151. At 104 C. 1.22 parts water dissolve one 
part salt; the solution then has a density of 1.265. 

Dilute solutions of f errocyanide are orange-yellow; concen- 
trated solutions are yellowish-brown. A solution of ferricyanide 
is decomposed in the light and on boiling, ferrocyanide being formed. 


It is precipitated from its solutions of alcohol. Under the influ- 
ence of heat it crackles, and is converted into ferrocyanide, 
nitrogen, cyanogen, Prussian blue, paracyanogen, and iron 

When burned in the flame of a candle it emits sparks of iron. 

Electrolysis and reducing agents, such as hydrogen sulphide, 
convert it into ferrocyanide: 

2Fe 2 (CN) i 2 K 6 + 2H 2 S = 3Fe(CN) 6 K 4 + Fe(CN) 6 H 4 + 2S. 

Nitric acid converts it into nitrate and nitroprusside of potassium. 
Bed prussiate peroxidizes the greater part of metallic oxides. 

Hydrochloric acid decomposes a solution of ferricyanide of 
potassium, transforming it into ferricyanide of iron. 

When treated with ammonia it yields ferrocyanide of potassium 
and of ammonium and nitrogen. It oxidizes phosphorus, sul- 
phur, sulphurous acid, and sulphites; it converts oxalic acid and 
oxalates into carbonates. Organic substances in general, and 
especially in the presence of ferric salts, likewise exert a reducing 
action on ferricyanide of potassium. All these reactions are very 
easily carried out if one operates in alkaline solutions. 

When a solution of a ferrous salt is treated with potassium ferri- 
cyanide a beautiful blue precipitate is obtained, which is called 
Turnbull's blue, Fe 5 (CN)i 2 +zH 2 0. This blue is distinguished 
from Prussian blue in that when it is heated with carbonate or 
hydrate of potassium it yields ferroferric hydrate and yellow prus- 
siate, while Prussian . blue under the same conditions yields ferric 
hydrate : 

Fe 5 (CN)i 2 +8KOH= 2[Fe(CN) 6 K 4 ] +Fe 3 (OH) 8 

Just as there is to the ferrocyanides a corresponding acid, hydro- 
ferrocyanic acid, so to the ferricyanides there is a corresponding 
acid, hydroferricyanic acid, Fe 2 (CN)i 2 H6, which, according to 
Friedel, may be represented by the following formula: 

HN=C O=N v > N=C 



Among the other interesting double cyanides must be mentioned 
the cobalticyanides, mangano- and manganicyanides, and finally 
the platino- and platinicyanides. 


Cobaltocobalticyanide is similar to TurnbulPs blue. Hydro- 
cobalticyanic acid is quite energetic, capable of decomposing car- 
bonates, of dissolving iron and zinc, setting free hydrogen, and 
of neutralizing alkali bases. The most interesting of the cobalti- 
cyanides are those of potassium, C02(CN)i2K 6 , an anhydrous salt, 
pale yellow, slightly soluble in water, insoluble in alcohol; of cop- 
per, Co 2 (CN)i 2 Cu3 + 7H 2 0, clear blue, insoluble in water and in acids, 
soluble in ammonia. The cobalticyanide of nickel, Co 2 (CN)i 2 Ni 3 + 
2H 2 0, blue when moist, green when dry, insoluble in water and 
acids, soluble in ammonia. 

The cobalticyanides are not toxic; they are in all respects analo- 
gous to ferricyanides. 


Manganocyanides are very unstable in air, which converts them 
into manganicyanides, which are likewise easily decomposable. Their 
solution is stable only in the presence of potassium cyanide. 


Platinocyanides correspond to the general formula Pt(CN) 6 M 2 . 
They may be considered either as combinations of cyanide of plati- 
num with a basic cyanide, or as the result of the union of a metal 
with the diatomic radical Pt(CN)e. 

Soluble platinocyanides are obtained by dissolving platinocy- 
anide hi an alkali cyanide, or else by precipitating platinous chloride 
with pot ssium cyanide. The other platinocyanides are obtained 
by double decomposition. 

Platinicyanides are obtained by the action of oxidizing agents 
on platinocyanides. Their mode of formation is doubtful; at present 
the best hypoth sis known is that of Hadow, who considers the platini- 
cyanides as a union of the platinocyanide with the oxidizing agent 
used in obtaining them. 



More stress will be laid on the double cyanides of gold, or auro- 
cyanides, on account of the impetus which they have given to the 
cyanide industry. Aurous cyanide unites easily with the cyanides 
of the other metals, yielding double cyanides, among which may 
be cited: 

(1) Aurosoammonium cyanide, Au(CN)2NH4, obtained by mixing 
saturated solutions of ammonium sulphite with auricopotassic cyanide. 
It is readily soluble in water and in alcohol. It is decomposed be- 
tween 200 and 250 C. 

(2) Aurosopotassic cyanide, or aurocyanide of potassium, 
Au(CN) 2 K, obtained by dissolving cyanide of gold, oxide of gold, 
or fulminating gold in potassium cyanide. It crystallizes in mother- 
of-pearl scales, is anhydrous, colorless, has a salty taste, is stable in 
air, soluble in 7 parts cold water, more soluble in boiling water, 
slightly soluble in alcohol, insoluble in ether. It is decomposed in 
a closed vessel, setting cyanogen free, and leaving ' a residue of 
potassium cyanide and gold. Acids break it up into aurous cyanide. 

Auricopotassic cyanide, or auricyanide of potassium, Au(CN)4K, 
occurs as large colorless, efflorescent crystals capable of being fused 
into a liquid which sets cyanogen free and leaves behind metallic gold. 


Nitroprussiates, or nitroferricyanides, are obtained when nitric 
acid acts on the ferro- or ferricyanides. According to Gerhardt, 
the formation of these compounds is due rather to the action of 
nitrogen dioxide which is formed by the nitric acid. 

This author ascribes to them the following formula : Fe(CN) 5 (NO)M 2 
or Fe 2 (CN)io(NO) 2 M4. They are non-saturated ferrocyanides, of 
which the radical CN is replaced by NO, or may be considered as 
ferricyanides where 2 (NO) replaces the group 2(CN)M. 

These salts are generally highly colored. Those of potassium, 
sodium, ammonium, barium, calcium, and lead are dark red, readily 
soluble, and distinctly cystaUine; those of copper, silver, zinc, iron, 
and nickel are insoluble. Alkalis decompose them, likewise does 
concentrated sulphuric acid; some of them dissolve Prussian blue. 
They give with sulphides purple color which is little stable. On 
heating them, nitrosulphides are produced. 



[ C= 27.90 

100CNOH= J:gJ 

H- 2.33 


Cyanic acid is an oxygen compound of cyanogen, which was 
discovered in 1818 by Vauquelin, later studied by Woehler and 

Its formula is CNOH. It is monatomic. It is a colorless liquid, 
'with sharp odor, the vapors of which irritate the eyes decidedly. 
It is soluble in water, but its solution readily breaks up into car- 
bonic acid and ammonia. Its solution in ether is the only one 
which is stable. When its alcoholic solution is heated it yields 
asters of allophanic acid. 

With metals it produces cyanates, salts which are quite stable 
when dry, except copper, mercury, and silver cyanates, but the 
presence of moisture breaks them up into carbonate and ammonia: 

2CNOM + 3H 2 = M 2 C0 3 + 2NH 3 + C0 2 . 

They are, as a rule, soluble. The cyanates of copper, mercury, and 
silver are only slightly soluble. 

Dilute acids decompose them into cyanic acid, but quite often 
into carbonic acid and ammonia. With concentrated acids, cyam- 
elide is formed. 

The alkali cyanates are obtained by igniting in air the corre- 
sponding cyanides, especially in the presence of metallic oxides, as, 
e.g., oxide of lead, manganese, or copper. 

C = 14.81 

100CNOK= 5:j 

K = 48.14 


Cyanate of potassium occurs as transparent anhydrous crystals, 
soluble in water. It is obtained, generally, by heating manganese 
dioxide with potassium ferrocyanide to redness. 


It is gradually decomposed by moist air and by water into 
carbonate of potassium and ammonium. 

Potassium dissolves in melted cyanate, yielding cyanide and 
oxide. Cyanate of sodium, CNONa, has analogous properties. 

Cyanate of ammonium is an isomer of urea, which it yields when 
heated at a moderate temperature, CNOH-NH 3 . 

Silver cyanate is white, readily soluble in ammonia and dilute 
nitric acid. When heated it explodes rather violently, leaving a 
residue of silver carbide. 


Cyanuric acid was discovered by Scheele and studied successively 
by Serullas, Woehler, and Liebig. It is obtained in many reac- 
tions, but the best method of producing it is that of Wurtz, which 
consists in passing dry chlorine through . melted urea and treating 
the residue successively with cold and with boiling water. It is 
a solid, crystallizing in octahedrons, odorless, tasteless, readily 
soluble in water, alcohol, and concentrated mineral acids. It is 
acid in reaction. It volatilizes at 360 C., when it is converted into 
cyanic acid. By prolonged boiling with concentrated acids it 
breaks up into carbonic acid and ammonia. 

With metals it yields tricyanates, which are only slightly soluble. 
They are decomposed by strong acids which set cyanuric acid free. 
When the tricyanates are heated they are converted into cyanates. 


Sulphocyanides, or rhodanides as they are sometimes called, are 
really sulphocyanates. They are formed by the union of sulpho- 
cyanic acid with a metal. This sulphocyanic acid is really cyanic 
acid in which the oxygen has been replaced by sulphur: 


For a long time it was wrongly considered as a hydrazid of the com- 
plex sulphocyanogen radical (CN)S. 

The sulphocyanides have the general formula (CN)SM. Most 
of them are soluble in water, alcohol, and ether, especially those 
of the alkali metals. They easily form double salts. As to the 


sulphocyanides of the heavy metals, they are insoluble, but are 
decomposed on boiling with the alkalis. Dilute acids decompose 
them even in the cold, with the exception of those of silver, mercury, 
and copper. In acid solution they are oxidized by permanganate 
of potash into hydrocyanic acid and sulphuric acid. 

Among the many sulphocyanides only the most important will 
be studied. 


f C = 12.37 

100(CN)SK- j *:JJ 
IK = 40.20 


This is an anhydrous, extremely deliquescent salt, crystallizing 
in prisms or in needles, of a density 1.886 to 1.906, very soluble in 
water and in alcohol (100 parts water dissolve 130 parts). Its 
solution in water is accompanied by an appreciable lowering of 
temperature (150 parts of this salt dissolved in 100 parts of water 
at 11 C. cause a temperature of. 23 C.). It has a fresh and pun- 
gent taste, but it is not poisonous. According to physiologists, it 
occurs in the human saliva. 

When ignited in air it is converted into potassium sulphate, 
though it is capable of withstanding a dull red heat for a long time 
without decomposition. 

Its aqueous solution undergoes a slow decomposition, which may 
be hastened by application of heat. Ammonia is set free. 

Chlorine and nitric aoid decompose it. When heated with a 
metal, potassium cyanide and a metallic sulphide are formed: 


This reaction has been used as a means of obtaining the alkali- 

Sulphocyanide of sodium, (CN)SNa, has analogous properties. 

Sulphocyanide of ammonium, (CN)SNH 4 , occurs in the form of 
deliquescent prisms readily soluble in alcohol and in water (105 
parts in 100 water). A mixture of 133 parts of this salt with 100 


parts of water at 13 C. causes a lowering of 31 in temperature. 
It melts at 159 C., and when heated to 170 C. it becomes trans- 
formed into sulphocarbamide : 

NH2 or thiourea. 
NH 2 . 

When subjected to dry distillation it is decomposed, yielding 
hydrogen sulphide, and sulphides of carbon and ammonia, leaving 
a residue of melam. It is capable of dissolving salts of sulphur. 

Silver sulphur cyanide is a white curdy precipitate, insoluble in 
water and ammonia, soluble in the sulphocyanides of ammonia and 
of potassium. 


By substitution of the group CN for OH hydrocyanic acid is 
capable with alcohols of forming hydrocyanic esters, which may 
be divided into two classes. In the first class, the alcoholic radical 
is attached to the carbon; in the second, it is attached to the nitro- 
gen. These are isomeric bodies; the 'former are called nitriles and 
correspond to the general formula R C = N; the latter are carbyl- 
amines or isonitriles, their formula being represented by R N = C. 
These are rather interesting bodies which should not be overlooked. 


Nitriles are derived from amides through dehydration. 

Nitriles possess general analogous properties whatever may be 
the atomicity of the alcohols from which they are derived; they 
form a clearly defined class of compounds. 

Nitriles have the following prope ties 

Under the influence of nascent hydrogen they fix 4 molecules 
of this element and form primary amines. 

Under the influence of dehydrating agents nitriles fix 2 mole- 
cules of water and are converted into ammonia salts of acids con- 
taining the same number of carbon atoms as the hydrocyanic acid 
ester used. Thus methyl cyanide gives ammonium acetate. 

They fix likewise one molecule of hydrogen sulphide in pro- 
ducing amido-sulphides. They unite with hydracids, with negative 
chlorides, and with bromides. 


The lowest member of the nitrile series is hydrocyanic acid, or 
formonitrile, H C=N. Among the most important may be cited: 

Methyl cyanide, or acetonitrile, CH 3 CN, a colorless liquid, lighter 
than water (sp. gr. 0.81-0.83), volatilizing at 77-78 C., having a 
pungent, aromatic, and ether-like odor. It is obtained by distilling 
ammonium acetate with anhydrous phosphoric acid. 

Ethyl cyanide or propionitrile, C 2 H 5 CN, is a colorless liquid 
having an alliaceous odor, sp. gr. 0.78, boiling-point 96.5 C. 

Propyl cyanide, or but yronit rile, CH 3 CH 2 CH 2 CN, having a 
density of 0.79 and boiling at 116 C. 

Butyl cyanide, C 4 H 9 CN, density 0.816, boiling-point 126 C.; 
amyl cyanide, C 5 HuCN; allyl cyanide, CH 2 : CH CH 2 CN, density 
.839, boiling-point 118 C.; cetyl cyanide, Ci 6 H 33 CN. 

The properties of the hydrocyanic esters of the second class, or 
carbylamines, are quite different from those of the nitriles. They 
are generally formed by the action of alkyl iodides on silver cyanide : 

Carbylamines are distinguished from nitriles, their isomers, by 
their odor, which is often disgusting, by their higher boiling-point, 
by their property of combining directly with acids, and finally 
by the action which hydrating and oxidizing agents produce upon 

In this case they yield, as do the nitriles, two products, one 
fixed, the other variable, according to the ester employed. But 
here the fixed product is no longer ammonia, and the variable product 
an acid more or less rich in carbon. The first is always formic acid, 
while the latter is an ammonium compound. Thus methylcarbyl- 
amine, ethylcarbylamine, amylcarbylamine yield, respectively, with 
hydrating agents, by fixing 2 molecules of water, methylamine, ethyl- 
amine, and amylamine. 


By its union with alcohol radicals, cyanic acid also yields cyanic 
esters, or alcoholic carbimides. The following only will be men- 

n TT , methyl cyanate, and butyl cyanate. 

These are mobile liquids, possessing repulsive odors and high boil- 


ing-points. Potash converts them into primary amines. It is ta 
Wurtz that we owe the discovery and study of these bodies. But 
these are not true cyanic esters. 

The true yanic esters were discovered by Cloez. They are 
isomeric with the esters discovered by Wurtz, but with this differ- 
ence, that under the influence of hydrating agents they no longer 
yield amines a,;jd carbonic acid as do the ' carbimides, but behave 
themselves as ordinary esters and yield the same alcohol as was 
used at the start, and a cyanate or tricyanate. Their density is. 
also somewhat higher. 





THE analytical properties hydrocyanic acid are the following: 

Silver nitrate : White precipitate soluble in ammonia and in 
boiling nitric acid. Iron s ts in the presence of alkalis: By adding 
potash and a few drops of a ferrous and a ferric salt to a hydro- 
cyanic acid solution there is formed a precipitate. If this be treated 
with hydrochloric acid, the oxide of iron dissolves, and the liquid 
remains dark blue, due to the Prussian blue in suspension. 

The following method can be used in the detection of even 
1 /20ooth part of hydrocyanic acid: To the liquid to be tested, 
add a little potash and a small amount of copper sulphate. This 
produces a precipitate of cyanide and hydrate of copper. By treat- 
ing this precipitate with hydrochloric acid the hydrate dissolves, 
leaving a white residue of copper cyanide. 

Liebig and Taylor's method is also quite delicate. This con- 
sists in converting hydrocyanic acid into ammonium sulphocy- 
anate, by heating it with ammonium sulphide until decolorized. 
On adding a drop of a ferric salt to this sulphocyanate a blood- 
red coloration is produced. 


Silver nitrate gives a white, curdy precipitate, soluble in excess 
of reagent, soluble in ammonium hydroxide, insoluble in dilute 
nitric acid. On igniting silver cyanide, it sets free cyanogen gas, 
burning with a purple flame. 

Ferrous-ferric salt gives a dirty-green precipitate with neutral 



solutions; a precipitate of Prussian blue and a ferrous-ferric oxide 
in alkaline solution. On addition of an acid the latter dissolves, 
leaving Prussian blue. Copper sulphide and tincture of guaiacum, 
if acidulated with a drop of hydrochloric acid, give an intense blue 

Acids give free hydrocyanic acid, recognized by its odor of bitter 

Calcium chloride: no precipitate. 

Ammonium sulphide when heated with cyanides and evaporated 
to dry ness, gives a red coloration on the addition of a ferric salt. 


Calcium chloride gives a precipitate in concentrated solutions. 
If the solution to be tested is only moderately concentrated, no 
precipitate occurs. Silver nitrate produces a reddish-brown pre- 
cipitate insoluble in nitric acid and in ammonia. 

' Ferrous sulphate produces a white precipitate, which on expo- 
sure to the air rapidly changes to blue by oxidation. Chlorine 
and nitric acid oxidize this precipitate instantly. 

Ferric chloride gives a precipitate of Prussian blue, insoluble in 
hydrochloric acid, but decomposed by boiling potash. 

Copper sulphate gives a brownish-red precipitate insoluble in 

Concentrated sulphuric acid, hot, sets free pure carbon monoxide. 
If the acid be dilute, hydrocyanic acid is set free. 


Silver nitrate gives an orange- yellow precipitate readily soluble 
in ammonia, insoluble in nitric acid. 
Calcium chloride: no precipitate. 

Ferrous sulphate produces a blue precipitate insoluble in HC1. 
Ferric chloride yields brown coloration. 

Copper sulphate gives greenish-yellow precipitate insoluble in HC1. 
Sulphuric acid gives same reactions as with ferrocyanides. 


Silver nitrate gives a white flocculent precipitate, soluble in excess 
of the reagent, slightly soluble in ammonia. 
Calcium chloride: no precipitate. 


Ferric chloride produces a blood-red coloration, stable in the pres- 
ence of HC1, but disappearing when exposed to heat or to the action 
of nitric acid, sulphurous acid, hyposulphites, or alkalis. 

Copper sulphate and sulphurous acid give a white precipitate of 
copper sulphocyanide insoluble in acids, soluble in ammonia. 

Lead acetate produces a crystalline precipitate which forms quite 

Sulphuric or hydrochloric acid produces no effect if the sulpho- 
cyanide solution be dilute and cold ; at the end of some time a yellow 
coloration takes place, and later a yellow precipitate of persulpho- 
cyanic acid; in warmth, carbon dioxide is set free, besides sulphide 
of carbon and hydrogen sulphide. 

Dilute nitric acid gives, in warmth, a yellow deposit of persulpho- 

Molybdic acid dissolved in HCl gives a red coloration which may 
be absorbed by ether. 


Silver nitrate produces a white precipitate which can be decom- 
posed by heat and is soluble in ammonia and in nitric acid. 

Lead acetate gives a white crystalline precipitate soluble in boiling 
water (distinct from that produced in hydrocyanic solution). 

Dilute and cold sulphuric acid yields carbonic acid possessing a 
pungent odor due to a mixture of this acid with non-decomposed 
cyanic acid. 




Liebig's Method. This is a volumetric method based on the 
following reactions: If to a solution of potassium cyanide is added 
a solution of silver nitrate, there is formed silver cyanide soluble in 
the potassium cyanide still remaining in the solution. Cyanide of 
silver is formed permanently only when all the potassium cyanide 
has been converted into the double cyanide. The appearance of 
the slightest amount of a permanent precipitate indicates the end 
of the reaction: 


CNK+AgN0 3 = CNAg+KN0 3 , (1) 

CNK+CNAg=(CN) 2 KAg, (2) 


2CNK+AgN0 3 = (CN) 2 KAg+KN0 3 . 

One molecule or 170 grams of silver nitrate requires therefore two 
molecules or 130 grams of potassium cyanide to form one molecule 
of the double cyanide of silver and potassium. A solution of silver 
containing 13.056 grams of pure silver nitrate per liter is prepared, 
and another solution containing one gram of potassium cyanide in 
100 cubic centimeters of distilled water is made, of which 10 cc. 
are used. Several drops of a solution of sodium chloride are added, 
and then the solution of silver nitrate is run in drop by drop until 
a permanent precipitation is formed. Each tenth of a cubic centi- 
meter of the silver nitrate used corresponds to one milligram of 
potassium cyanide. Three or four titrations should be made and 
the average taken. 

This method is applicable to solutions of hydrocyanic acid, which 
must first be saturated with potash. 

If the cyanide . contains chlorides, the method is not accurate. 
In this case the gravimetric method is preferable. The solution of 
cyanide is precipitated by silver nitrate, the precipitate is filtered, 
washed, dried, and weighed. Then it is boiled with HC1, which 
converts the silver cyanide into silver chloride. This is filtered, 
washed, dried, and weighed again. From the increase in weight may 
be calculated the quantity of cyanide. 1 gram CNK should give 
2.058 grams CNAg. 

Fordos and Gelis' Method. This method is to be recommended. 
It is based on the ability of potassium cyanide to decolorize a solu- 
tion of iodine in alcohol or in potassium iodide. The reaction is 
as follows: CNK+I 2 = KI + CNL That is, there is a formation 
of potassium iodide and of cyanogen iodide, both of which are 
colorless. The end of the reaction is indicated by the yellow colora- 
tion of iodine in excess; 

The iodine solution is prepared by dissolving 40 grams pure 
iodine in one liter alcohol of 33. Five grams of the cyanide to 
be analyzed are dissolved in 500 cc. distilled water. 50 cc. of this 



solution are transferred to a 2-liter flask, to which is added 1 
liter of water and 100 cc. seltzer- water. The addition of this 
carbonated water converts the bases and carbonates to bicarbon- 
ates, which do not absorb iodine. Then the iodine solution is added 
drop by drop, stirring constantly, till the yellow coloration char- 
acteristic of iodine dissolved in potassium iodide appears. 

From the volume of iodine solution used must be subtracted 
the quantity of cyanide, knowing that 254 parts of iodine are absorbed 
by 65 parts of potassium cyanide. If, at the end of the titration, 
the solution, colored by several drops of iodine in excess, has a tur- 
bid instead of a transparent appearance, this is an indication of 
the presence of alkaline sulphides. In this case it is best before 
titrating to remove the sulphides of the alkalis by means of a 
solution of lead acetate or of zinc sulphate, filtering and washing 

The following table, calculated by Fordos and Gelis, gives the 
percentage of cyanide directly: 




















































































































































































































There are numerous methods, but only the most interesting 
and the best adapted, either in manufacturing or in gold-mining, 
will be cited. 

Commercial potassium cyanide quite often contains impuri- 
ties, such as the carbonate, sulphate, cyanate, formate, sulphide, 
ferrocyanide, sulphocyanide, and sometimes chloride of potassium. 
Carbonates may be detected by dissolving the salt in water and add- 
ing acids, which will cause effervescence, or adding lime-water, 
which will produce a turbidity. 

Cyanates may be detected in two ways: ," 

(1) By extracting the salt with alcohol of 84 and adding con- 
centrated hydrochloric acid to the alcoholic solution, when car- 
bonic acid will be set free; or 

(2) By adding ammonium chloride to the alcoholic solution 
and boiling urea is formed, which may be separated by evaporating 
to dryness on the water-bath, and taking up the residue with 
alcohol. When urea is acted upon by an alkaline hypobromite, 
nitrogen is set free. 

Formates may be detected by adding several drops of mercuric 
chloride to a boiling solution of cyanide, when, if formates are pres- 
ent, there will be produced a precipitate of calomel. 

Potassium sulphide may be detected by the aid of lead salts, 
which give a black precipitate. If the cyanide contains ferro- 
cyanide, its aqueous solution will give a precipitate of Prussian 
blue with a ferric salt (pure cyanide gives a greenish precipitate). 

Sulphocyanide may be detected by treating the solution with 
a slight excess of HC1 and then with ferric chloride, when a red 
coloration will be formed. 

Chlorides may be detected by precipitating the solution with a 
slight excess of silver nitrate, and then boiling the precipitate in 
nitric acid. If the precipitate completely dissolves, there are no 

Analysis of Cyanates. (Method of 0. Hertig, Zt. fur angew. 
Chem. 1901, p. 619.) The method is based on the decomposition 
of cyanates by hydrochloric or sulphuric acid, with formation of 
an ammoniacal salt: 


(1) CNOK+2HC1 + H 2 = KC1+NH 4 CH-C0 2 . 

(2) 2CNOK + 2H 2 S0 4 + 2H 2 = (NH^ 2 S0 4 4- K 2 S0 4 + 2C0 2 . 

Dissolve 0.2-0.5 gram cyanide in a porcelain dish in several 
cubic centimeters of water. Add either dilute HC1 or H 2 S0 4 and 
evaporate to dryness. Take up with water. The solution contains 
ammonia, which may be determined by boiling with soda, the ammo- 
nia being driven off and collected in n/5 sulphuric acid, which is 
afterward titrated, using fluorescein as indicator. 

Determination of Potassium. If this is done by means of plati- 
num chloride, after the cyanates have been decomposed with 
HC1, the presence of ammonium chloride may lead to errors. It is 
necessary in this case, after the cyanates have been decomposed 
by HC1, to drive off the ammonia at a dull red heat in a platinum 


This method is based on the fact that when a solution of hydro- 
cyanic acid or an alkaline cyanide containing an excess of ammonia 
is treated with a solution of copper salt, there is first formed a double 
salt of copper and ammonium, which is colorless. When the reac- 
tion is complete, the ammonia acts on the copper salt added and 
gives the characteristic blue color. This indicates the end of the 
reaction, which takes place as follows: 

4CNNH 4 + CuS0 4 = (NH 4 ) 2 S0 4 + Cu(CN) 2 ,2CNNH 4 . 

For this purpose there is used a copper-sulphate solution containing 
23.102 grams of the pure crystalline salt, free from efflorescence, 
per liter of water. Take 1 cc. of the medicinal hydrocyanic acid, 
or 100 cc. of the laurel-cherry or bitter-almond extract, or 0.5 gram 
of alkaline cyanide dissolved in about 100 cc. water, and to such a 
solution add 10 cc. ammonia, and stir. Then add, drop by drop, 
the solution of copper sulphate, stirring constantly, till the blue color 
becomes permanent. Each drop of the copper solution produces 


at first a pinkish spot, which later changes to a delicate purple when 
the end reaction is near completion. At this point the further 
addition of copper salt must be done with care. This method is 
scarcely applicable except for cherry water-extract. It gives results 
which are inexact, especially if a too large amount of water be added; 
because the cuproammonium cyanide may be decomposed by water. 
It happens sometimes that even in the titration of the cherry solu- 
tion there is formed, from the first, a permanent violet color, which 
interferes with the delicacy of the reaction, especially at the end. 
This may be remedied by the addition of carbonate of ammonia 
(10 cc. of a solution containing 1 part ammonium c rbonate, 4 parts 
water, and 1 part strong ammonia). 


Erlenmeyer's method is the one most generally used in the deter- 
mination of ferrocyanide. It is based on the precipitation of ferro- 
cyanide as Prussian blue. It is both rapid and 'accurate. 

Another method is based on the following : When an acidified 
solution of commercial ferrocyanide is treated with potassium per- 
manganate, the potassium ferrocyanide alone produces an oxidation 
product capable of reproducing the raw material under the influence 
of ferrous oxide in alkaline solution, while none of the other oxidized 
substances are at all affected by this same ferrous oxide. 

The mode of procedure is as follows : 3 grams of ferrocyanide are 
dissolved in water in a 500-cc. graduated flask. The solution is 
acidified with sulphuric acid, and then a concentrated solution of 
potassium permanganate is added until a permanent red coloration 
is obtained after several minutes 7 shaking. The solution is allowed 
to stand one-half hour. Caustic soda is then added in large excess, 
and the solution brought to the temperature of boiling water, with 
constant stirring. To the hot solution sulphate of iron is added 
till a black precipitate of magnetic iron oxide is produced. The 
solution is cooled, made up to 500 cc. with water, and filtered. In 
an aliquot of the filtrate, acidified with sulphuric acid, ferrocyanide 
is determined by titrating with potassium permanganate. This 
method requires about one hour. 

There is another method, based on the insolubility of potassium 


feirocyanide in dilute alcohol, but it is applicable only when the 
solution contains at least 15% ferrocyanide. 

To 70 cc. of 95. alcohol, acidified with acetic acid, 10 cc. of the 
ferrocyanide solution is added. The ferrocyanide is precipitated 
as a crystalline powder, which may easily be separated by filtra- 
tion. After washing with 95 alcohol, the filter is dried at 100, 
the precipitate redissolved in water and titrated with permanganate. 


The solution of sulphocyanide is precipitated with a standard 
solution of silver nitrate, using a ferric salt as indicator. 

The blood-red color disappears as soon as there is an excess of 
silver solution showing the end of the reaction. 

Or the reverse may be done, and this latter procedure is pre- 
ferable: To a solution of sulphocyanide add an excess of standard 
silver nitrate, and titrate this excess with standard sulphocyanide. 
In this case the end of the reaction is indicated by the appearance 
of the permanent red coloration. 


Knubblauch's Method (1889). This method consists in trans- 
forming insoluble compounds into a soluble salt, purifying this 
product, and titrating the ferrocyanide therein by means of a 
copper salt. 

250 grams substance are dried at 50-60 C. for 6 hours. The 
dried mass is passed through a sieve (360 meshes per sq. cm.). 10 
grams of the sifted material are transferred to a graduated 255 cc. 
flask, and 50 cc. n/10 solution of potash added. Allow the solu- 
tion to stand, with frequent shaking, for 15 hours. Fill the flask 
up to the 255-cc. mark and filter. 100 cc. of filtrate are added to 
an hydrochloric acid solution of ferric chloride (60- grams FeCls 
in 200 cc. HC1 sp. gr. 1.19, and solution made up to a liter). The 
precipitate is rapdily filtered through a folded filter and washed 
with hot water. The filter and precipitate are transferred to a 
250-cc. flask and treated with 20 cc. n/10 potash in order to con- 
vert the Prussian blue into ferrocyanide of potassium. The solu- 


tion is then made up to 250 cc. and filtered. If filtrate contains 
no hydrogen sulphide, it is acidified and then titrated with a standard 
copper solution. If the filtrate contains hydrogen sulphide, it is 
advisable to add 1-2 grams lead carbonate, shaking, and filtering. 
100 cc. of this filtrate (1.6 grams original material) are acidified 
with 5-6 cc. n/5 sulphuric acid and then titrated with the following 
copper solution: 

Water 1000 cc. 

Copper sulphate 12-13 grams, 

which is standardized by means of a solution of potassium ferro- 
cyanide containing 4 grams of the pure salt per liter. The end 
of the reaction is noted by taking up a drop of the solution and 
moistening filter-paper which has been treated with ferric chloride. 

Moldenhader and Leybold's Method (1889). This consists in 
decomposing the ferrocyanides by evaporating them with sulphuric 
acid, and determining, by means of permanganate, the iron in the 
sulphate of iron remaining, after having previously converted it 
into the form of protoxide salt. 

Place 50 grams of the finely pulverized substance in a liter flask 
with 100 cc. of an n/10 solution of soda, containing also 2% anhy- 
drous sodium carbonate. Let the flask stand in a warm place for 
4 or 5 hours, then make up the solution to 1030 cc. Shake, filter, 
and evaporate 100 cc. of the filtrate in a porcelain dish to 10 cc. 
Transfer these 10 cc. to a platinum dish, add 25 cc. n/10 solution 
of H 2 S0 4 , being careful of a too lively effervescence. Evaporate 
dry on a sand-bath, and heat the dish to redness. The residue in 
the dish is a mixture of ferric sulphate and bisulphate of sodium. 
Cool, and dissolve the mixture in rt/10 sulphuric acid, washing out 
the dish with this n/10 sulphuric acid, so that about 100 cc. in all 
may be used, then rinse with 50 cc. hot water. Make up the solu- 
tion to 250 cc., add 10 grams pure zinc and 1 cc. ?i/10 copper sul- 
phate solution. Heat on water-bath 3 hours; this reduces com- 
pletely the ferric sulphate (test with potassium sulphocyanide) . 
Cool, filter and dilute to 400 cc., and titrate with permanganate to 
a slight pink (deduct 0.4 cc., due to the same quantity of water, acid, 
copper, and zinc, in blank determination). From the number of 
cubic centimeters of permanganate used, the amount of ferrocyanide 
or of Prussian blue found in the spent oxide may be easily calculated. 


Burschell's Method. Treat 20 grams of the dried and pulverized 
mass ; moistened with a little water, with 200 cc. of a solution of 
potassa (1-2). Shake and let stand several 'hours, then make up 
to 260 cc. (10 cc. extra due to the volume of the mass), shake and 
filter. Add 100 cc. of the filtrate to a solution of ferric alum dis- 
solved in hot sulphuric acid. Filter the Berlin-blue precipitate, wash 
with hot water, and then transfer paper and precipitate to a 500-cc. 
flask. Add a little water, 15 grams mercuric oxide, and 1 gram 
ammonium sulphate. Heat to boiling for about a quarter of an 
hour, and after cooling add 1 cc. of a saturated solution of mer- 
curous nitrate, Hg2(N03)2, and ammonia so long as a precipitate 
is formed. Make a solution up to 500 cc., shake and filter. Transfer 
200 cc. of the filtrate to a 400-cc. flask, add 6 cc. ammonia (sp. gr. 
0.9) and 7 grams zinc powder (the cyanogen in cyanide of mercury 
is thus transposed, and recombined as ammonium cyanide), shake 
for a few minutes, then add 2 cc. of a 30% solution of potassia and 
make up to 400 cc. Shake and filter. 

Allow 100 cc. of the filtrate ( = 0.875 gram original substance) 
to run into an excess of n/10 solution silver nitrate (40 cc. are gen- 
erally enough) contained in a 400-cc. flask. Add dilute nitric acid 
and make up to 400 cc. Filter and titrate 200 cc. of the filtrate 
with an n/20 solution of ammonium sulphocyanide after first adding 
5 cc. of a saturated solution oi iron alum. 

The end of the reaction is indicated by a clear brown colora- 
tion. 1 cc. Ti/10 silver- nitrate solution corresponds to 0.007042 gram: 
Fe(CN) 6 K 4 +3H 2 or to 0.003832 gram Prussian blue. 

Zaloziecki's Method (Zt. fur angew. Chem. 1890, p. 210). 20 
grams of the dry, pulverized purifying material are transferred to 
a 100-cc. cylinder with 20 cc. of a 10% solution of potassa. Heat 
on water-bath one half -hour, cool, make up to 100 cc.; take 45 cc., 
which corresponds to 10 grams original substance (assuming that 
the 20 grams occupy a volume equal to 10 cc.), and heat over free 
flame till no more ammonia is set free. Neutralize the solution 
exactly with dilute HC1 or H 2 S04, using phenolphthalein as 
indicator. When the solution is neutralized, add 20 cc. normal 
potassium carbonate and 5 grams moist zinc carbonate, heat 
one half-hour while passing a stream of carbonic acid through the 


After cooling, dilute to 100 cc., and titrate 50 cc. ( = 5 grams 
substance) with n/10 acid, using methyl orange as indicator. 

By deducting the amount of acid equivalent to 10 cc. potassium 
carbonate normal solution and multiplying the remaining number 
of cubic centimeters by 0.46, the per cent of potassium ferrocyanide, 
Ee(CN) 6 K 4 +3H 2 0, is obtained. 

E. Donath and B. M. Margosche's Method (Zt. fur angew. Chem. 
1899, p. 345). This method is based on the fact that the ferro- 
cyanides and ferricyanides of the alkalis are easily decomposed, in 
alkaline solution, by oxidizing agents. 

The whole of iron separates as ferric oxide, and this element 
may be quite accurately determined in the precipitate, by known 
methods. The following is the mode of procedure: 

Grind the purifying material quickly in an iron mortar. Transfer 
50 grams into a liter flask, add 100-150 cc. of a 15% solution of 
caustic potash Allow the flask to stand in a warm place for some 
time, shaking frequently. Complete the volume to 1030 cc. and 
filter through a folded filter. To an aliquot part of the filtrate add 
a bromated solution of caustic soda (prepared by dissolving 80 
grams of sodium hydrate in water, cooling and making up to 1000 cc., 
and adding 20 cc. of bromine, shaking thoroughly). Heat for some 
time. Under these conditions there is formed an abundant, thick, 
pulverulent precipitate of a beautiful brick-red color, together with 
a lively liberation of gas. Let the precipitate settle several hours, 
filter and wash. It may be dissolved on the paper with hot dilute 
HC1 and the iron reprecipitated with ammonia. But it is preferable 
to dry the precipitate on the paper, then to transfer it to a small 
flask, to burn the paper, and fuse the ash thus obtained with potas- 
sium bisulphate, and to add this product to the remainder of the 
precipitate in the flask. The whole is then dissolved in dilute sul- 
phuric acid. Reduce with zinc and titrate the iron by means of 
potassium permanganate. 

The amount of iron multiplied by 7.5476 gives the quantity 
of crystallized salt, K 4 Fe(CN) 6 +3H 2 0, or multiplied by 6.5833 
gives the amount of anhydrous salt. 



Method of Dr. Nauss of the gas-works at Carlsruhe. 
This is based on the decomposition of Prussian blue by alkalis, 
which are combined as follows: 

= 4Fe(OH) 3 +3Fe(CN) 6 Na 4 . 

Prussian blue is treated with hot caustic soda, the reaction being 
complete when the green coloration has disappeared. 

The following is the mode of procedure: 

Weigh 10 grams of the material and place in a 500- cc. flask con- 
taining 50 cc. of a 10% solution of caustic soda. Shake often, 
and allow the flask to stand at ordinary temperature till the whole 
of the blue has been decomposed by the caustic alkali. This requires 
about 15 hours. The formation of sodium sulphide is avoided 
if a dilute solution of soda be used. When the decomposition is 
ended make solution up to 505 cc. with water (the 5 cc. extra are 
for the volume of iron oxide). Shake thoroughly and filter. Take an 
aliquot part e.g. 50 cc. = 1 gram substance add 10-15 cc. of a hot 
acid solution (consisting of 200 grams ferric alum, one liter water, 
and 100 cc. sulphuric acid) in order to decompose the sodium ferro- 
cyanide contained in the Prussian blue. Heat on water-bath till 
the pungent odor is no longer apparent and filter through a funnel 
surrounded with hot water. Wash with hot water till the filtrate 
is free from sulphuric acid. The residue which contains all the 
Prussian blue is transferred to a flask to which water is added. 
Bring the solution to boiling, stirring continually. The quantity 
of blue may then be determined with a solution of sodium hydroxide. 
It is necessary in order to decompose the whole of the blue to add 
successively the required amount of n/5Q solution. The decom- 
position takes place rapidly if the solution be heated several moments, 
and the excess of the sodium hydroxide may be titrated anew against 
n/50 acid. The reaction is ended when the green coloration is per- 


Substances in which the existence of cyanogen compounds is 
suspected are finely divided and diluted with distilled water so 
as to form a light pulpy mass. This is acidified with tartaric or 


phosphoric acid (acids which have no action on hydrocyanic acid, 
but capable of setting it free from cyanides). This mixture is 
placed in a tubular retort provided with a straight safety-tube 
and connected with a bent tube which plunges to the bottom of 
a double tubular Woolf bottle. This latter is connected with a 
bulb-tube. Both of these contain a dilute solution of silver nitrate. 
Heat gently on the water-bath so as to produce a slow ebullition, which 
must be carefully watched. Under these conditions the presence 
of hydrocyanic acid is shown by the formation of a white precipi- 
tate of silver cyanide in the Woolf bottle and in the bulb-tube. 
When the precipitate no longer increases the distillation is stopped. 
Cool and unite the solutions of the bulb-tube and the bottle; filter, 
wash, dry at 100 C., and weigh. 

But as quite often substances to be analyzed contain hydro- 
chloric acid, which would give a perfectly analogous precipitate, 
it is well to make sure, by means of the ordinary reactions which 
we have already described, that one has really to do with cyanogen 
or its compounds. 

Moreover, it is to be noted that cyanide of mercury gives neither 
the reactions of mercury nor those of the cyanides. One may 
either precipitate the mercury with hydrogen sulphide, filter, and 
test for hydrocyanic acid, as indicated above, or else, and this is 
preferable, plunge blades of iron for a sufficient length of time into 
the extracted solutions of the substances suspected, which have 
been acidified with sulphuric acid. The mercury is precipitated 
by the hydrogen and the cyanogen converted into hydrocyanic 




IN order to complete this general study it seems necessary to 
give some thermochemical information relative to the principal 
cyanated compounds. 

The following outline is taken from Berthelot's remarkable 
work Sur la force des matieres explosives, d'apres la thermo- 
chemie (t. II., p. 64, etc.): 


The heat of formation of cyanogen determined by Berthelot 
by ordinary combustion or by detonation is 

C 4 (diamond) + N 2 = C 4 N 2 -74.5 cal. 1 

From this number Berthelot draws the following conclusions: 
" Cyanogen (C 2 N), as well as acetylene (C 2 H) and nitrogen dioxide 
(N0 2 ) and all substances which play the role of true compound 
radicals, is a body whose formation is accompanied by the absorp- 
tion of heat, a circumstance which seems to be of such a nature as 
to explain the very character of this real compound radical, mani- 
festing in its combinations a greater energy than in its free elements. 
The energy of these latter becomes stronger rather than weaker 
because of this absorption of heat, as is the case in combinations 
which give off heat, and this increase of energy renders the com- 
pound system comparable to the most active elements." 

x The same notation is used in this chapter as that used in Berthelot's work. 




The heat of formation of hydrocyanic acid, determined by vari- 
ous methods by Berthelot, may be expressed thus: 

C 2 (diamond) +N + H = C 2 NH (gaseous) = -29.5 cal. 
= C 2 NH (liquid) = -23.8 "' 
= C 2 NH (dissolved) =-23.8 ff 

" It follows from these figures/' says Berthelot, " that hydro- 
cyanic acid is formed from its elements with absorption of heat, 
which explains the readiness with which this acid forms direct 
combinations, polymeric compounds, and brings about complex 

Berthelot remarks further that " cyanogen and hydrocyanic 
acid, acetylene, etc., could be regarded as formed with liberation of 
heat, if it were admitted that carbon, when considered as diamond 
or charcoal, does not correspond to the real elementary carbon, 
which should be comparable to hydrogen and probably gaseous, 
while the diamond and charcoal represent its allotropic modifica- 
tions. In passing from its gaseous to its polymeric and condensed 
state, elementary carbon would liberate a considerable quantity 
of heat, and greater than the heat absorbed in the formations of 
acetylene (-30.5 cal. for C 2 = 12), and of cyanogen (-37.3 cal.)" 

The actual figures show that the formation of hydrocyanic gas 
starting with cyanogen and hydrogen is 

Cy + H = CyH liberates + 7.8 cal. 

" This formation is therefore exothermic," a circumstance which 
led Berthelot to foresee that it could be brought about directly; 
and, in fact, the illustrious savant did succeed, contrary to the 
negative experiments previously worked out by Gay-Lussac, in 
combining the two gases directly under the influence only of time 
and heat. The synthesis of hydrocyanic acid by means of acetylene 
and nitrogen, both in the free state, by the electric spark, which 
was discovered by Berthelot in 1868, liberates +2.1 cal. 



The heat liberated by the formation, from its elements, of solid 
cyanide of potassium, determined by Berthelot, is as follows" 

C 2 + N + K = C 2 NK crystallized liberates + 30.3 cal. 

The direct formation of potassium cyanide, by means of the 
union of its elements, in the same proportion by weight as repre- 
sented by the equation, cannot be brought about, in fact, at the 
ordinary temperature. But it is admitted that it does take place 
at a very high temperature, if free nitrogen is made to act upon 
charcoal impregnated with potassium carbonate, that is, under 
the conditions where nascent potassium is formed. 

" At this temperature cyanide of potassium is a liquid, per- 
haps even gaseous, change of state which absorbs heat, but on the 
other hand the potassium is gaseous, which fact somewhat com- 
pensates. If the free nitrogen, carbon, and potassium really do 
combine, without other intermediary reaction, as, e.g., the formation 
of an acetylide (which has not been proved), one will have to admit 
that the total synthesis of cyanide of potassium liberates heat under 
the real conditions in which it is effected. 

" Whether the liberation is produced all at once or only by 
successive reactions, it explains the total synthesis no less. 

" The union of cyanogen with potassium takes place, as is known 
directly. This union calculated for the following states: 

Cy (gas) +K (solid) = KCy (crystallized) liberates + 67.6 cal. 

" This figure justifies the direct synthesis of cyanide of potassium 
by means of cyanogen, but the heat liberated is less than that liberated 
in the union of the same metal with the gaseous halogen elements." 

The latter is 

C1+K = KC1 = 4-105.6 cal. 
Br gas + K = KBr = + 100.4 rf 
I solid + K = KI = + 85.4 < r 
= KCy=+ 67.6 " 

Berthelot attributes to this inferiority in the amount of heat 
liberated the decomposition of solutions of potassium cyanide by 


the halogens, and further says that " the cyanogen which should 
be set free is combined moreover with one half of the halogen body, 
not without a slight liberation of additional heat ( + 1.6 cal. for 
yCl gas, +4.2 cal. for Cyl solid). Then he compares the quan- 
tities of heat liberated when starting with the hydracids and dilute 

yH (dilute) + KO - OH (dilute) = KCy dissolved + H 2 2 = + 3.0 cal., 

which is a quantity much less than that liberated in the formation 
of the chloride, bromide, or iodide of potassium ( + 13.7 cal.). With 
gaseous hydracids the disagreement is still greater ( + 17 cal.). 
Berthelot concludes from this that " hydrocyanic acid is a much 
weaker acid than the hydracids derived from the halogen elements, 
and that it is even displaced in potassium cyanide dissolved by 
most of the acids. 

" The transformation of potassium cyanide into potassium 
formate : 

C 2 NK (dissolved) +2H 2 2 = C 2 HK0 4 dissolved + NH 3 dissolved, 
liberates +9. 5 cal. 

" That is the reaction which goes on slowly in solutions of potas- 
sium cyanide. 

" The same reaction carried on on the dry salt by water- vapor 
produces formate, and also ammonia gas. It is much more rapid, 
but it also liberates twice the amount of heat, +17.7 cal. If the 
temperature is raised, this reaction becomes complicated because 
of the subsequent destruction of the formate by heat or by an excess 
of alkali, a reaction which takes place at about 300 and which 
transforms completely potassium cyanide into potassium carbonate: 
C 2 NK solid + KO- OH solid + 2H 2 2 gaseous 

= C 2 4 +2KO solid +NH 3 gas - liberates +37.4 cal. 

" I call attention to this because it is one of the most active 
causes of the destruction of potassium cyanide during its manu- 
facture, where one works with the fused salts, a fact which slightly 
modifies the figures above, without modifying the general signifi- 
cance of them." 



The formation of solid ammonium cyanide starting with gaseous 
hydrocyanic acid and gaseous ammonia liberates +20.5 cal. ; and 
starting with the elements +40. 5 cal. 


Because of the difficulty in obtaining pure hydroferrocyanic 
acid Berthelot determined the heat of formation of this acid 
in an indirect way, i.e., by displacing it from its salts by a more 
energetic acid. 

" By mixing a dilute solution of potassium ferrocyanide, CysFeK^ 
= 4 liters, with dilute hydrochloric acid (1 equiv. = 2 liters), no 
change of temperature is observed; either there is no reaction, or 
the two acids liberate the same quantity of heat in combining with 
the potassa, in which case the base in the solution could be divided. 
The latter case is the more likely. In fact, by mixing ferrocyanide 
with dilute sulphuric acid a progressive separation and a displace- 
ment which tends to become complete, in the presence of a large 
excess of sulphuric acid, are observed. Thus 

Cy 3 FeK 2 (6 liters) +HS0 4 (1 equiv. = 2 liters) liberates +1.107 cal. 
Cy 3 FeK 2 (6 liters) +2HS0 4 (1 equiv. = 2 liters) liberates +0.181 cal. 

By continuing the gradual addition of sulphuric acid an absorption 
of heat is produced, due to the formation of bisulphate. 
"With a large excess added all at one time 

Cy 3 FeK 2 (4 liters) +10HS0 4 (1 equiv. = 2 liters) liberates +0.966 caL 

" These phenomena are comparable to the reaction of sulphuric 
acid on the chlorides, although the results are somewhat different. 
Here likewise is a progressive division of the base between the two 
acids. If it be admitted that the 10HS04 be sufficient to remove 
almost the whole of the potassa from the ferrocyanide, similar to 
that which is produced with the chlorides, nitrates, etc., the heat 
x liberated in the reaction of dissolved hydroferrocyanic acid on 


dilute potassa may be calculated. In fact, +15.7 cal. being the 
heat liberated in the reaction of sulphuric acid on potassa, and 
-1.75 cal. the heat absorbed in the reaction of dilute 4HS0 4 on 
dissolved potassium sulphate (formation of bisulphate), the desired 
reaction will be 

4(Cy 3 FeH 2 =4 liters) +KO(1 equiv. = 2 liters) liberates 
x = + 15.71 - 1.75 -4(0.97) = + 13.5 cal. 

" This figure is practically the same as that which represents, 
the heat liberated by hydrochloric acid and nitric acid when acting 
on potassa, from which it follows that hydroferrocyanic acid is a 
strong acid comparable to the mineral acids. It is known that 
it displaces carbonic and acetic acids. The absence of apparent 
thermic reaction between HC1 and dissolved cyanoferride is in 
harmony with these results. 

" Nothing is easier than passing through that to the formation 
of Prussian blue; in fact 

i(Cy 3 FeK 2 =4 lit.)+S0 4 Fe(l eq. = 2 lit.) = -JCy 3 Fefe precipitated 
+ KS0 4 dissolved liberates +2. 54 to 2.78 cal., 

the amount of heat liberated increasing with length of time, as often 
happens in the formation of amorphous precipitates. Likewise 

| (Cy 3 FeK 2 = 4 lit.) + N0 6 fe(l eq. = 2 lit.) =iCy 3 Fefe 2 precipitated 
+ KN0 6 dissolved liberates + 0.725 cal. 

" From the results obtained with ferric sulphate, the substitu- 
tion of potassa for iron peroxide (KO for FeO) in Prussian blue liber- 
ates +7. 2 cal.; from the results obtained with the nitrate, +7.2 cal., 
a perfect agreement. 

" By admitting that the formation of cyanoferride of potassium, 
CyFeH 2 (dilute) +2KO dilute, liberates + 13.5x2 = 27.0 cal., it is 
thereby concluded that the formation of Prussian blue with the 
same acid and precipitated peroxide of iron, 

Cy 3 FeH 2 + 2f eO (precipitated) liberates + 6.3 X 2 = 126 cal. 


" The value 6.3 differs but little from 5.7, which represents the 
union of nitric and hydrochloric acids with iron peroxide, which 
fact is a new proof of the analogy between hydroferrocyanic acid 
and the mineral acids. Nevertheless +6.3 is greater than +5.7, 
which fact explains why dilute hydrochloric acid does not decom- 
pose Prussian blue with formation of iron chloride. 

" Hydrocyanic acid, one of the weakest acids known, has formed 
therefore, by its association with iron cyanide, a powerful acid, 
comparable in all points to hydrochloric and nitric acids. 

" This is a new proof calculated to establish the fact that the 
best characterized acid properties, even in the hydrocarbon com- 
pounds, are not necessarily connected with the presence of oxygen. 

" The heat liberated in the formation of cyanoferride itself 
remains to be determined. 

"I found the following results: S0 4 Fe(l eq. = 2 lit.) +280^6 
(1 eq. = 2 lit.)+6KO(l eq. = 2 lit.) liberates 23.2 cal. By adding 
to the above mixture 3CyH(l eq. = 4 lit.) a further liberation of 
+ 39.3 cal. is observed, which represents the formation of cyano- 
ferride, starting with CNH and the two oxides: 

3CyH (dissolved) +2KO (dissolved) + FeO (precipitated) 
= Cy3FeK 2 (dissolved) liberates 39.3 cal. 

" As a control experiment, I added to the solution 3HC1 
(1 eq. = 2. lit.), which liberated +25.0 cal., with the formation of an 
abundant precipitate of Prussian blue, the heat liberated varying 
during the precipitation from 23.0 to 25.0 cal. 

" In short, HC1 has produced the following reactions: 

HC1 dilute +KO dilute = KC1 dilute + 13.6 cal. 
2HC1 f( +feOppt. =2feCl " +11.4 "! 
2f eCl ' '' + Cy 3 f eK 2 dissolved = 

Cy 3 Fef e 2 +2KC1 dilute + 1.4 "' 

26.4 cal. 

" The agreement between 25.0 and 26.4 is as close as one may 
expect when working with similar precipitates, the state of which 
varies with the conditions. 


" From that I conclude 

SCyH dilute + FeO ppt . + 2f eO ppt . = Cy 3 Fef e 2 ppt . liberates + 24.9 cal. 
3CyH dilute + FeO ppt. = Cy 3 FeH 2 dissolved + 12.3 cal. 

" I verified these values by forming Prussian blue directly by 
means of CNH and the two sulphates: 

3CyH(l eq. = 2 lit.) +S0 4 Fe(l eq. = 2 lit.) +80*16(1 eq. = 2 lit.) 
= Cy 3 Fef e 2 ppt. + 3HS0 4 (dilute) liberates + 37.5 cal. 

" The difference between the heat of formation of alkali sul- 
phate and that of iron sulphate starting from the oxides being 

12.5 + 11.1-47.1= -23.5 cal., 

and the heat of formation of 3CyK starting from potassa being 
+8.9 cal., from these data the heat liberated in the formation of 
Prussian blue from CNH is easily found: 

3CyH dilute + FeO +2feO = Cy 3 Fefe 2 
liberates +37.5 + 8.9-23.2= +23.2 cal., 

a result which shows sufficient agreement with +24.9 cal., obtained 
in another way, but which I regard as a little less exact. 

" Let us draw some general conclusions from these results. The 
first conclusion is in regard to the heat liberated in the formation 
of cyanoferride, starting with hydrocyanic acid or with potassium 
cyanide : 

SCyH (dissolved) +3KO dilute liberates +8.7 cal. 

SCyH (dissolved) +2KO + FeO ppt. liberates +39. 3 cal. 

" The substitution of ferrous oxide for potassa with formation 
of cyanoferride liberates a large amount of heat, i.e., +39.3 8.7 
= +30.6 cal. One single equivalent of ferrous oxide contributes, 
moreover, to the formation of hydroferrocyanic acid. 

1 This .figure explains, besides, the observed displacement^ and 
it corresponds to the constitution of a new molecular type, that 
of hydroferrocyanic acid. 

" In fact, we conclude from that 


3CyH (dissolved) +FeO ppt. liberates + 12.3 cal., a quantity 
greater than the heat (+9.0 cal.) liberated by 3KO (dilute) united 
with 3CyH. 

" That is because here there are two simultaneous reactions: the 
union of 3 mol. of CNH into a type thrice as much condensed, and 
the combination of ferrous oxide which enters the constitution of 
this new type Cy 3 FeH 2 . 

", Likewise, in the case of Prussian blue, it has elsewhere been 
established that Cy 3 FeH 2 (dilute) +2feO ppt. liberates + 12.6 cal. 
= 6.3X2, i.e., practically the same number as the union of the same 
oxide with dilute HC1 and HN0 3 . 

" Starting from CNH itself we have 

3CyH (dilute) +FeO+2feO = Cy 3 Fefe 2 ppt. +24.9 cal. = 8.3X3. 

" The magnitude of this last figure, which is three times the 
heat liberated when potassa unites with hydrocyanic acid, is the 
explanation, as above, of the formation of the new molecular type 
of cyanoferrides, and still more so of the formation of the double 

" This superposition of effects explains, moreover, the superiority 
of apparent affinities which the oxide of iron shows over potassa 
in its union with hydrocyanic acid, which is shown by a greater 
liberation of heat than in the formation of ordinary oxysalts, sul- 
phates, nitrates, acetates, etc., starting with the dilute acids and 
alkaline bases corresponding to the metallic oxides. 

" Would it not be possible to find some analogous circumstance 
to explain how the oxides of silver and of mercury, besides the 
oxides of iron, liberate more heat than does dilute potassa in uniting 
with hydrocyanic acid? That is, are the cyanides of silver and 
of mercury really represented by the simple formulas CyAg, CyHg, 
salts comparable to those of CyK and CyH, or else would it not 
be better to regard them as a more condensed type of cyanides, 
such as 

Cy 2 Hg 2 and Cy 2 Ag 2 ? 
" The heat liberated by their union with cyanide of potassium 


in the formation of double cyanides, even in the state of dilute solu- 
tions, such as 

Cy2HgK, Cy2AgK (rough formulas), 

would support this supposition, for it would be the result of the 
passage from the simple type, cyanide of potassium, to the com- 
plex type which constitutes the double cyanides, 

Cy 2 Hg 2 + 2KCy = 2Cy 2 HgK ; 
Cy 2 Ag 2 + 2KCy = 2Cy 2 AgK 

" Besides, hydrocyanic acid is not the only acid which is the 
occasion of a general overthrowing of the ordinary affinities, inter- 
preted by the corresponding thermic effects between the alkaline 
oxides and the metallic oxides. Hydrogen sulphide is in exactly 
the same case. 

" Notwithstanding these latter considerations it remains no 
less a fact that the metallic oxides liberate more heat than the alka- 
line bases, uniting with hydrocyanic acid, a fact which explains 
why they displace them. Thermochemistry thus takes into account 
the constitution of the complex cyanides, new molecular types, 
which are very superior to the primitive type because of the energy 
of their affinities in regard to the bases, as well as because of the 
stability of the resultant salts I mean very superior to hydrocyanic 
acid, which contributes to their formation by condensation. 

" Hydrocyanic acid, common generant of condensed types, is 
distinguished, moreover, because it is formed from the elements 
with an absorption of heat 29.5 cal.; in other words, its formation 
has stored up an excess of energy which makes it specially fit for 
successive combinations and molecular condensations. 

" Let us give, finally, the heat of formation of potassium ferro- 
cyanide from its elements: 

Fe+K 2 +Cy3 = Cy 3 FeK2 (solid) liberates + 183.6 cal. or 61.2x3. 
From simple bodies: 

Fe+2K+3C+3N = C 3 N 3 FeK 2 +71.7 cal. or 23.9X3. 

These results are close to those which are obtained in the forma- 
tion of potassium cyanide, starting with cyanogen +67.6 cal., and 
with the elements +30.3 cal. 


" The hydrated salt encloses 3 molecules of H 2 0(3HO), extra, 
whose union in the liquid form with the anhydrous salt liberated 
+ 2.48 caL, which brings the total amount of heat liberated in the 
formation of the crystalline yellow prussiate from the elements and 
H 2 0, +94.2 cal." 


The formation of solid potassium cyanate from the elements is 
C 2 diamond + N + K + 2 = C 2 NK0 2 liberates + 102.0 cal. 

The dissolved salt liberates + 96.8 cal. 

The same formation starting with dilute KOH: 

C 2 + N + OKO dilute = C 2 NK0 2 (dissolved) liberates + 15.5 caL 

From gaseous Cy: 

Cy + K + 2 = CyK0 2 solid + 139 . 3 cal. 

Cy + + KO dilute = CyK0 2 dissolved +51.8 rr 

Cy 2 +2KO dilute = CyK0 4 dilute + CyK dilute + 34.2 "' 

All these results are greater than the heat liberated in the analo- 
gous reactions of the real halogen elements, e.g., 

C1 2 gas + 2KO dilute = C10 2 K + KC1 dissolved liberates only + 25.4 caL 

There is, moreover, this difference, that the complex nature of 
Cy and its tendency either to form polymeric and other condensed 
bodies, or to regenerate ammonia and its derivatives, are the cause 
of a number of secondary reactions, such as do not occur in the 
case of chlorine. These reactions are easier in proportion as the 
heat liberated by the direct reaction is greater and in proportion 
as it furnishes from that time a greater reserve of energy by other 

" The union of dry potassium cyanide with gaseous oxygen in 
the formation of solid cyanate C 2 NK (solid) + 2 (gas) = C 2 N0 2 K 
(solid) would liberate +102.0-30.3= +71.7 cal., a large figure, 
and about three fourths of the heat (+94.0) liberated by the com- 
bustion of the carbon contained in the cyanide. 

" This figure refers to bodies taken in their actual state, a fact 
in which, up till now, no absorption of oxygen by the cyanide of 


potassium has been observed, probably because it has not been 
investigated. In the fused state, on the other hand, it easily takes 
place, as is known. Now these figures just calculated may be 
approximately applied to the same bodies, under the known con- 
ditions of their real reaction, at a high temperature, for the fusion 
of the cyanide as well as of the cyanate should absorb about equal 
quantities of heat. 

" Considering the heat liberated by the oxidation of its potassium 
compound, cyanogen agrees more with iodine, and differs, on the 
contrary, with chlorine. We have in fact: 

KC1 + 2 = KC10 4 (solid) absorbs -ll.Ocal., 

KBr + 4 = KBr0 4 " " -11.1 " 

KI + 4 = KI0 4 " liberates + 44.1 rr 

= KCy0 2 "' " +71.7 

a progression inverse to that which characterizes the union of a 
like metal, such as K, with the same series of halogen bodies, such 
as Cl ( + 105.0 caL), gaseous Br ( + 100.4 cal.), gaseous I (+85.4 cal.), 
and cyanogen (+67. 6 cal.) 

" From the preceding figures is explained why cyanide of potas- 
sium has such a great tendency to oxidation, either under the influ- 
ence of oxidizing agents, or even n air. 

" The combustible character of one of the elements of cyanogen 
opposes, moreover, the formation of peroxidized acids, as with 
chlorine, and the halogen elements such compounds would have too 
great a tendency to being converted into carbonic acid. 

" The complete combustion of solid potassium cyanate, 

C 2 NK0 2 + 3 = CO K+C0 2 + N, would liberate +83.9 cal. 

"The facility with which potassium cyanate becomes regenerated 
from ammonia, even from the one fact of its long contact with 
water, is easily explained : 

C 2 NK0 2 + 2H 2 2 

= C0 3 K (dissolved) +C0 2 NH 3 HO dissolved liberates +20.0 cal. 

"That is also an amide reaction. 

"The well-known transformation of fused cyanate of potassium 


by means of water-vapor into fused carbonate of potassium, car- 
bonic acid, and ammonia liberates about +9 cal. 

"'The conversion of potassium cyanide into carbonate and am- 
monia under the combined influence of oxygen and water-vapor 
at a high temperature, a conversion so pernicious in the industrial 
preparation of prussiates, is no less easily explained by thermo- 
chemistry. In fact, at the ordinary temperature we should have 

C 2 NK solid +0 2 +3HO gaseous 

= C0 3 K solid +C0 2 gas +NH 3 gas +79.3 cal. 

At about red heat this figure should remain likewise large, the 
cyanide and the carbonate being partially fused." 

For the thermochemical data referring to cyanogen and its com- 
pounds see the tables at end of the book. 





THE development of the industry of the cyanated compounds 
is due, as was stated in the Introduction, primarily to the use of 
potassium cyanide in the treatment of auriferous minerals. 

At first the production of cyanides was, so to speak, insignificant, 
or at least limited. The industry was created in 1710 with the dis- 
covery of Prussian blue, by the dyer Diesbach, and for a long time 
was limited to this c mpound used in dyeing. The discovery of 
potassium ferrocyanide and the other cyanogen compounds came, 
but later, and among these the ferrocyanide alone was applied in 
the arts and manufactures. Cyanide of potassium did indeed have 
for a time a certain limited market in photography, but its poisonous 
properties and its relatively high price made it give place to hypo- 
sulphite of sodium. From that time it was a laboratory and phar- 
maceutical rather than an industrial product. But as a result of the 
remarkable researches of MacArthur and Forest, some fifteen years 
ago, in the extraction of gold by means of potassium cyanide, this 
salt became industrially important, giving to the whole industry 
of the cyanide compounds an impetus and a vitality which made 
it acquire rapidly its present development, which is still bound to 


The application of these methods brought about as an immediate: 
consequence a considerable increase in the consumption of cyanide 
of potassium to such an extent that in 1898 this consumption arose 
to 3300 tons, and in the month of August of that year the demand 
was S3 great that the German manufactories which produce the 
major part of this product were unable to fill their orders punctually, 
notwithstanding the price had been advanced 29% to the English 

In June 1899 the national bureau of foreign commerce was in 
possession of data from Johannesburg showing a consumption of 
450,000 English pounds of cyanide per month, which amount repre- 
sented a value of $135,000, delivered. 

It is quite probable that these figures would still have increased had 
it not been for the war in South Africa, and the consumption in that 
country alone would have arisen to 10,000 tons. 

The result of . this development is easy to foresee. The work 
was undertaken most zealously; the manufacturers in England 
and in Germany especially sought means of producing the cyanide 
in sufficient quantities to supply the demand, and under the most' 
economical conditions, as shall be seen when the study of the various 
meth ds is taken up. An active s ruggle was established among 
the manufacturers of cyanide, the result of which has been infinite 
progress in this industry. Even at the present time numerous 
researches are being undertaken along these lines, and it is to be 
hoped that these efforts will not be fruitless, but rather a process 
will be found which will permit the production of potassium cyanide 
under conditions remunerative both to the producer and consumer. 
The industry of the cyanide compounds has been developed especially 
in Germany and in England; France has remained somewhat behind 
in this line. Several manufacturers produce some cyanide, to be 
sure, but they do not find such an outlet for it as they should have, 
because of the great competition in the market which the English 
and the Ge mans are making, and because of the cheaper price 
at which they sell their product. 

This condition of affairs attracted the attention of the Min- 
ister of Commerce and Manufactures, and in a letter of Dec. 
6, 1897, addressed to the President of the Council Chamber of 
Chemical Products, he called to the attention of the manufactur- 


ers the important markets reserved for this branch of chemical 

The letter, as well as the discussion which it provoked at the 
meeting of the Council Chamber of Chemical Products on the 8th, 
of December following, are here reproduced: 

PARIS, December 6, 1897. 

The export house Orosdi Back, whose headquarters are in Paris, cite- 
d'Hauteville, No. 9, recently called my attention to the interest which the: 
manufacture of potassium cyanide would offer to French industry. 

The use of this product in treating the wastes of gold-mines has giveir 
such results that all the mines are gradually making installations for putting; 
this method into practice. 

The present sales of potassium cyanide in the Transvaal and, the whole of 
South Africa already exceeds 3000-4000 tons per annum, and it is expected 
within two or three years, when the cyanide process shall have become general, 
that the demand for this product will exceed 10,000 tons in the Rand district 
alone. If to this amount be added the quantity consumed by all the gold- 
mines in all parts of the world, it is seen that a considerable field is open for 
the sale of this product, the sale of which at present is monopolized by England 
and Germany. 

According to Orosdi Back, the cyanide of potassium employed should 
be 98%, of a pale-yellow color. It is shipped in wooden boxes lined with zinc, 
holding 100 kg. The price varies from 190 to 230-240 francs per 100 kg. 
It seemed to me that the above data would be of interest to your association, 
and I have the honor of communicating them to you, giving you the care 
of making them knowji to the manufacturers who might be willing to use 

Yours, etc., 

Minister of Commerce, Industry, Post, and Telegraph. 
For the Minister, by authority. 

Director of Commerce, 


Council Chamber of Chemical Products, sitting of Dec. 8, 1897. 

Before receiving this letter the Minister had already interviewed me on 
this question, and I explained to him that the French manufacture of potas- 
sium cyanide is only enough for our needs, i.e., about 30,000 kg. per year; 
that this amount is produced y a single firm, other manufacturers who pro- 
duced it formerly having abandoned it because of the unremunerative price 
obtained for it. 

The price of potassium cyanide has, in fact, suffered a considerable reduc- 
tion in the last few years. At present it is worth 3 francs per kg. in France, 
and 2.25 francs in England and Germany. 


The consumption of this product is very great in the Transvaal, but the 
figures 3000-4000 tons, given by the firm Orosdi Back, seem somewhat ex- 
aggerated. From data which I have received, the sales in the Transvaal 
would amount to 100 tons per month, and only 1 ton in Madagascar; but 
the consumption of this colony is destined to increase. 

The company in France which manufactures potassium cyanide tried to 
compete with foreign firms doing business in the Transvaal, but abandoned 
the attempt because it was estimated that the sale price of 2.25 francs per 
kilogram (about 22.5 cents per Ib.) did not leave a sufficient profit. 

MR. GASTON POULENC: The English have found, and are now exploiting, 
processes for the manufacture of potassium cyanide without the use of ferro- 
cyanide. That is a very great advantage when the net cost is considered. 
And this superiority will last until our manufacturers or our chemists have 
analogous met hods. 

MR. PRESIDENT: It seems to me, finally, that the communication just 
presented by our fellow member fully confirms the data which I gave to the 
Minister, and the inability of the French industry to compete successfully 
^t the present time. 

It is to be hoped that in the near future the discoveries of our chemists 
will make it possible for us to regain this industry. The effort of the inventors 
is i this direction, and in the last dozen years, both in France and abroad, 
a great number of patents for the production of this substance have been 
taken out. 

Having made these general observations, let us now examine the 
state of this industry in the different countries where cyanide is 

The following table shows the production of the different coun- 
tries in 1899, according to L. Guillet: 





Germany Austria 



1 500 




2 000 




United States 


1 500 

Belgium Holland . 






France therefore produces l / 2 i of the total production of cyanides 
and 1 /7 of the ferrocyanides, while Germany and England produce 
more than 1 / 2 of the total of these two products. 

The consumption is found divided among the different countries. 

Ferrocyanide of potassium which is produced in France is to 


a great extent exported to Germany and England, where it is trans- 
formed into the cyanide. Germany herself exports a* great quantity 
to the United States, where for economic reasons it is transformed 
into the cyanide of potassium; the remainder is us d at the manu- 
factory for the various needs of the industry. The cyanide is exported 
to gold-mines, notably to the Transvaal, where its consumption 
increases daily. Thus in 1897 the consumption in the Transvaal 
was 1710 tons; in 1898 it had increased to 2230 tons; in 1899 to 
2400 tons. The other gold districts consume but little because 
the beds are still worked by the old method and quite often they 
are not in the hands of companies or manufacturers, the gold being 
bought from individual workers. 

However that may be, the cyanide method is gradually increasing. 
Several installations in the United States, in California and Alaska, 
have been noted, and one can foresee that gradually the total con- 
sumption wi 1 be considerably increased. 

The following table gives the names of the principal firms of 
France and other countries which manufacture or sell cyanide com- 








near Bo 
ille, nea 

illiers (Se 

La Ne 

SllltS^ ^35 g 

If I 

I ^ 

I ^ 3 g 

|"3 ^ w'S 'I 




i-ggg jx 






c3 0) 

t lrl 





5 * 



. .H3 - . 

. . fl . . . . 


. . 3 . . . . 



. . C . oj 




o ' HH 

. . ^ .0 


: :.- :l 




6 -' 

go o !^, " 



- -b 

1 11 f 

Q IrfS S^-iS^e3s^^^3 








f Products 

|C 2 2 2 2 2 


Sw ,.*, 




1 I 







GERMANY Continued. 



l|||l|j"l ; i||il|ll ; 








cj 6 

S o ' ' ' 

-g ^ ::::::::::::::: 



Ifil-Mi iNNN 




^ :::::. 


^ -] Q'S^l' co S- ! 


3 :::::: 


^ddcS^^^li- l ~ < O-^ 

^ t+-i S "S ~| "2 '. O"Q ^ S ^ ' 

p| j ; 


British Cyanides Comp 
Dolbbe & Son 
Foster & Son 
Harris & Co., Limited. 
Hopkins & Williams. . 
Johnson & Sons 



O z 





c ^ 2 ^ a <-, 



i Ng* 


.a > 






H- 1 

'S a 







Hochstetter & 
Engel und Becke 

S -S 

i w l 


^ 05 w 







Although it is extremely difficult to obtain data from the manu- 
facturers concerning the production and consumption, the net cost, 
etc., we have, nevertheless, been able to procure a certain num- 
.ber of documents bearing on these questions. The following tables 
give a sufficiently correct idea of the condition of the cyanide indus- 
tries, and show well the development of this branch of chemical 
industry during the past few years. 




' Country. 















186 404 




343 574 


150 028 

% 65 


216 753 







243 488 


100 932 





260 941 







254 803 

1893 . . . 

50 771 




239 510 

1894 . . . 





216 695 






232 906 






228 402 







125 559 







87 696 






86 873 

1901 (10 months). 




















104 354 


76 699 

181 105 


84 458 


62 701 

147 224 




11 477 

81 822 

1891 . 



14 212 




. . 



83 919 











15 705 

50 478 




32 883 

92 879 








33 764 






12 022 

18 634 


13 272 

21 899 

1901 (10 months). 





FROM 1897-1900. 







45 339 

115 531 

87 470 

71 A A A 


41 878 



4.C1 QO/i 


41 879 

40 017 


47 979 


22 293 



17 1R^ 

Other countries 
Colonies and Protectorates 

United States 


of which 2,189 
for Algeria. 


of which 20,000 
for Reunion. 



55 917 



40 328 




463 124 

645 697 

Value in francs 



717 842 

1 065 400 

FERROCYANIDE, 1887-1896. 






Amount in kilograms . 
Value in francs 




215 397 

363 044 






Amount in kilograms. . 
Value in francs . 




216 986 

232 014 

FERROCYANIDE, 1887-1896. 







Amount in kilograms. . 
Value in francs 











Amount in kilograms. . 
Value in francs 









BEFORE taking up the discussion of the numerous methods 
for the manufacture of the cyanide compounds, it seems necessary 
to glance for a moment at the evolution accomplished by these 
methods, a very interesting evolution, since it has transformed 
an industry which was at first entirely subjected to the crudest 
empiricism to an industry based on purely scientific data. 

The industry of the cyanogen compounds, like that of the greater 
part of the chemical industries, had its origin in alchemy. It orig- 
inated in 1704, from the discovery of Prussian blue. This dis- 
covery, which was purely accidental, is due to the Berlin dyer Dies- 
bach, who obtained this compound by the action of alum and sul- 
phate of iron on the potash residues which the then celebrated 
alchemist Dippel had used in the rectification of an animal oil extracted 
from the volatile substances of blood. 

From this discovery, Dippel concluded that Prussian blue was 
formed by the action of iron on potassa which had been brought 
in contact with organic animal substances at a certain temperature. 

The discovery of Diesbach immediately became of industrial 
importance, and Prussian blue was prepared by calcining dried 
beef's blood, and later meat or horns with potassium carbonate. 

The product of this treatment was extracted with water, and 
the solution thus obtained, called blood-lye, was treated with alum 
and sulphate of iron, giving Prussian blue. This was for a long 



time the only body known and prepared, and th's without knowing 
exactly what was its composition and its mode of formation. 

In 1752 Macquer, then Bergmann and Sage, showed that from 
Prussian blue a definite and crystallizable salt could be extracted, 
the nature of which they could not determine. 

That Prussian blue and the salt obtained from blood-lye were 
compounds of cyanogen was first definitely proven in 1823 by Gay- 

Although this was an important discovery, yet the methods of 
producing these compounds were not at all changed, and for a long 
time the only method employed, notwithstanding its imperfec- 
tions, was that of igniting nitrogenous organic substances in the 
presence of alkaline carbonates. That method sufficed, more- 
over, to supply the limited demand. 

But, beginning with 1837, a most interesting and important 
series of discoveries and researches in the history of the cyanide 
industry attracted the attention of investigators and manufac- 
turers, and fixed in a clearer manner the ideas which were being 
formed concerning the formation of these bodies. The successive 
discoveries of Clark and of Redenbacher, describing the formation 
of efflorescences of potassium cyanide in blast-furnaces, together 
' with the works of Lewis Thompson, Desf osses, Fowner, and Young, 
who obtained this same compound by the action, at red heat, of 
a current of air upon a mixture of potassium carbonate and char- 
coal, gave birth to the first principles of a theory which at first 
was disputed, but soon after acknowledged to be the true one. 

In fact, several -years later, Bunsen, then Playfair, and later 
Riecken, in their investigations established clearly the role which 
atmospheric nitrogen plays in the formation of cyanide compounds. 

It is easy to understand how this discovery attracted the atten- 
tion. of the manufacturers when the importance and the economic 
aspects of the question are considered. From that time on they 
exerted themselves in applying in a practical way the results ob- 
tained by investigators, and numbers of patents followed each 
other, all tending to do away with the use of nitrogenous organic 
matter (which is rather costly and imperfect) and approaching as 
much as possible to the synthetic production, which is simpler and 
more economical. 


At the present time the tendency is still in the same direction, 
and one must not despair of seeing, in the very near future, the 
success of this important problem of the fixation of atmospheric 
nitrogen in the production of cyanide compounds on an industrial 

The first efforts in this direction were unfortunately fruitless 
and therefore short lived. They were all inspired with the same idea : 
the passing of nitrogen over a suitably heated mixture of charcoal 
and an alkaline carbonate or an alkali. Such are the methods of 
Bunsen, Ertel, Armengaud, Possoz, and Boissiere, Lambilly. 

The next step was the replacing of the carbonates of the alkalis: 
by the alkali metal itself (Castner, MacDonald, Mackey, Hornig, 

Other inventors made use of ammonia instead of nitrogen. Quite 
recently, in Germany, processes have been patented along this line,, 
and, as will be seen later, the results are thought to be satisfactory. 

Indirect means were also tried, such as those suggested by Gelis,. 
and taken up by Tcherniac and Gunzberg, which consisted in pro- 
ducing ammonium sulphocyanide, and this was converted into potas- 
sium cyanide. 

In the mean time the discovery of cyanide compounds in the 
purifying masses from the manufacture of illuminating-gas, and in 
sugar-beet molasses and vinasses, added a new and lively interest 
to this industry. 

One must also mention the use of metallic carbides recently 
praised as a means of fixing atmospheric nitrogen for the production 
of cyanides, a tentative method which seems to have given some 

That the question is complex may easily be seen from these general 
remarks. It has not yet been definitely solved, nor has the ideal 
process been found. Nevertheless certain modes of manufacture 
have already furnished appreciable results, and show a real progress.. 
All these will be reviewed in this portion of this work. 

The order in which this interesting study will be taken up follows 
quite naturally from the preceding remarks and will be as follows : 

Chapter VI. Manufacture of Cyanides. 

(1) Non-synthetic processes: (a) production by means of f erro- 
cyanides; (6) production by means of sulphocyanides. 


(2) Synthetic processes : (a) the use of atmospheric nitrogen ; 

(6) the use of ammoniacal nitrogen. 

(3) Other processes. 

Chapter VII. Manufacture of Ferrocyanides. 

(1) Old processes. 

(2) Extraction of gas residues: (a) direct extraction of the 

gas; (6) extraction of ammoniacal liquors; (c) extrac- 
tion of the spent oxides from illuminating-gas. 

Chapter VIII. Manufacture of Ferricyanides. 

Chapter IX. Manufacture of Sulphocyanides. 

Chapter X. Manufacture of various other cyanide compounds : 
nitroprussiates, Prussian blue, Turnbull blue, etc. 



Old Process. The oldest method of obtaining potassium cyanide, 
a method which is scarcely ever used except in the manufacture of 
the absolutely pure salt, is that of Robiquet, modified by Geiger. 
It consists in igniting the dried yellow prussiate or ferrocyanide of 

Under the influence of heat the ferrocyanide of potassium is 
decomposed according to the reaction 

Fe(CN) 6 K 4 = 4CNK + C 2 Fe + N. 

It is absolutely essential that the ferrocyanide of potassium 
used for this purpose should be (1) perfectly free of sulphate uf 
potassium, which in the above reaction would become transformed 
into the sulphide, which would give a yellow color to the cyanide; 
(2) perfectly free from its water of crystallization, which would tend 
to retard the reaction. 

The method of preparation is as follows: Yellow prussiate is 
first carefully dried at about 100 C. upon plates of sheet iron or 
in cast-iron pans; thus the dried product is transferred to forged- 
iron crucibles capable of holding about 80 liters and covered with 
an iron lid. These crucibles are then placed in batteries of five or 
six in furnaces. 

Into each one are placed 80 kilograms of ferrocyanide and the 
whole gradually heated. Just as soon as the product is fused, the 
temperature is gradually raised to a dull red; the whole is stirred 



from time to time with a long-handled iron dipper. The operation 
lasts about seven or eight hours, and is ended when a sample taken 
out and cooled has a white, dull, porcelain-like appearance. 

Care must be taken that the temperature does not go beyond 
dull redness, otherwise the cyanide formed would itself be decom- 
posed into potassium carbide and nitrogen. 

2CNK = C 2 K 2 +N 2 .* 

When the operation has been carefully carried out, the result is 
a mixture of carbide of iron and cyanide of potassium, the former 
adhering to the sides of the crucible, the latter in the midst of the 

In order to obtain the cyanide from the mixture recourse may 
be had to decantation followed by filtration or to lixiviation. 

In the first case the fused product is decanted upon cast-iron 
niters (A) (Fig. 1), the bottom of which is a grate which is covered 
to about 1 / 3 of the height of the filter with iron turnings. This filter 
is kept at dull redness during the time of the operation. The cya- 
nide is drawn from the crucibles by means of iron dippers and 
poured upon the filter. The first portions of the filtrate are often 
contaminated with carbide of iron; they are therefore fused anew 
in the crucibles and there refiltered. 

The filtrate is collected in polished and perfectly clean iron pans 
(C), which are set in a trough (D) filled with cold water. 

Too long contact of the potassium cyanide with the iron carbide 
formed must be avoided, for experience has shown that the ferro- 
cyanide was inclined to become once more formed by an inverse 

If recourse is had to lixiviation, the product of ignition is taken 
up either with water or with alcohol. 

The extraction with water is a cheaper but a more delicate 
operation. Much care must be taken and the work carried on 
rapidly, because water always decomposes the potassium cyanide, 
forming ferrocyanide. 

* It may be remarked that it is precisely this decomposition of potassium cyanide 
at a high temperature which renders it impossible to obtain the cyanide by means 
of the electric furnace, as was attempted by Moissan. 



Although the use of alcohol is quite costly, it is preferable. The 
extraction is carried on in the warmth; it is quite slow because 
of the little solubility of potassium cyanide in alcohol. 

In each of the above cases, the lixiviation is followed by evapora- 
tion and a rapid drying of the cyanide. In the case of alcohol 
this solvent may be recovered and so be used over and over. 

As may be seen this process is rather defective. During the 
process notable quantities of cyanogen in the form of iron carbide 
and nitrogen are lost, and in fact only about 2 /3 of the cyanogen 
used is recovered; 10 parts of ferrocyanide give only 7 parts of 

FIG. 1. Cyanide-filter. 

cyanide, i.e. 45 kg. of absolutely pure cyanide for 100 kg. ferrocy- 
anide used. 

Liebig's Process. With a view of remedying this objection,. 
Clemm Rodgers and later Liebig proposed igniting dry ferro- 
cyanide in the presence of dry potassium carbonate. This process, 
is still sometimes used. Clemm advised the use of a mixture of 
8 parts ferrocyanide and 3 parts potassium carbonate. The reac- 
tion is as follows: 

(1) Fe(CN) 6 K 4 + C0 3 K 2 = 6CNK + FeO + C0 2 , but under the influ- 
ence of the iron oxide formed a smaU quantity of cyanide is trans- 
formed into cyanate, so that the reaction is in reality as follows: 

(2) Fe(CN) 6 K 4 +C0 3 K 2 = 5CNK+CNOK+Fe+C0 2 , or, better 
still, a combination of equations (1) and v (2). 

2Fe(CN) 6 K 4 +2C0 3 K 2 = 11CNK +CNOK + FeO +Fe +2C0 2 . 


The product is treated with water whereby a solution is obtained 
consisting of cyanide and an excess of potassium carbonate. 

In order to separate these bodies, alcohol or acetone is added 
which precipitates the insoluble cyanide. 

The residue, consisting of iron oxide, potassium carbonate, iron, 
small quantities of undecomposed ferrocyanide and unprecipitated 
cyanide, is powdered and allowed to stand in air. Under these 
conditions insoluble iron peroxide is formed. The product is once 
more extracted, the solutions evaporated, and the residue ignited. 
In this way a certain part of the potassium carbonate may be 
recovered which may be used over again. Ten parts of ferrocyanide 
give 8.8 parts cyanide and 2.2 parts of cyanate. 

Wagner's Process. In order to avoid the formation of cyanate 
at the expense of cyanide, Wagner proposed igniting the mixture 
of ferrocyanide and alkali carbonate with a small quantity of finely 
pulverized wood charcoal the use of which is to reduce any cyanate 
formed. The following are the amounts proposed by Wagner: 

Ferrocyanide of potassium 8 parts. 

Carbonate of soda 2 

Powdered wood charcoal 0.2 part. 

The reaction is 
Fe(CN) 6 K 4 + C0 3 Na 2 + C = 4CNK + 2CNNa + Fe + C0 2 + CO. 

Another advantage of this method would be the separation of 
iron, which would be easier. The mixture thus obtained is formed 
by 4 mol. of potassium cyanide and 2 mol. sodium cyanide. Later 
will be discussed the advantage which this mixture, which is richer 
in cyanogen, has over potassium cyanide alone. 

Chaster's Process. This is only a modification of Wagner's 
process, and consists in adding to the mixture of ferrocyanide car- 
bonate and charcoal a certain amount of tar, pitch, or bitumen. 
The yield is thus somewhat greater, the reaction being carried on 
in the reducing atmosphere produced by the hydrocarbons added. 

The following are the proportions proposed by Chaster: 

Anhydrous ferrocyanide 65-75 parts. 

Carbonate 20 " 

Wood charcoal. . 5 ' c 


The ferrocyanide and carbonate are ground together and during 
the grinding 5% dried wood charcoal is added, together with a 
quantity of tar, pitch, bitumen, or asphaltum or any other analogous 
substance sufficient to give the whole mass the consistency of a 
paste or of mortar. In case the mass may not be plastic enough 
a small quantity of benzine or petroleum is added. 

This mass is compressed into the form of briquettes, which are 
ignited in a furnace with a reducing flame. 

Notwithstanding these modifications, processes which are based 
on the decomposition of ferrocyanide under the influence of heat 
are not profitable. They are rather costly; the losses in nitrogen, 
in alkali, and even in cyanide by volatilization are sometimes con- 

Their industrial use haSv always been most limited. In trying to 
perfect these processes, many very ingenious modifications have 
been devised which have, it seems, given good results, and the 
industrial use of which has, latterly, been quite extensive. 

The Process of Rossler and Hasslacher (of New York). The type 
of these new modifications is that of the house of Rossler und Hass- 
lacher of New York, belonging to the Deutsch Gold und Silber 
Scheide Anstalt. This process, which was proposed by Erlenmeyer, 
is based upon the action of metallic sodium on potassium cyanide, 
according to the reaction / 

Fe(CN) 6 K 4 +Na 2 = Fe+4(CNK),2(CNNa). 

The product is then treated with water and the solution evaporated. 

The product thus obtained, which is sold as potassium cyanide 
98-100%, is in fact but a mixture of 4 mol. of potassium cyanide 
with 2 mol. sodium cyanide, a product identical with that produced 
by Wagner's process. If the whole be assumed as potassium cyanide, 
it is seen that it contains 98% of the cyanogen used. Moreover, 
this mixture has the advantage of being richer in cyanogen than is 
the potassium cyanide, because the atomic weight of sodium is. 
less than that of potassium. Thus 109 grams of this mixture cor- 
responds to 106 grams of potassium cyanide. 

Besides having the advantage of avoiding loss of cyanogen, this 
method permits the use of metallic sodium, a metal which, since- 


Deville's process for the manufacture of aluminium was abandoned, 
found but little use in the arts. 

At present, sodium is produced on a large scale by electrochem- 
ical industries; it is therefore of interest to call attention to this 
method of application. This process is, moreover, in considerable 
use in England, Germany, and even in France. 

Wichmann and Vautin's Process. Because sodium was still 
rather expensive, attempts were made to replace it with alloys of 
alkali metals with lead. These alloys are at the present time 
obtained much cheaper than the alkali metals, by subjecting fused 
alkali chloride to electrolysis in a bath of melted lead, which acts as 
a cathode. 

In order to obtain potassium cyanide, a mixture of potassium 
ferrocyanide with a lead-potassium alloy is used. If the sodium 
cyanide be desired, sodium ferrocyanide and a lead-sodium alloy 
are taken. 

As in the Rossler and Hasslacher process, a double cyanide of 
sodium and potassium may be prepared, by causing an alloy of 
lead sodium to act upon potassium ferrocyanide, or a lead-potassium 
alloy to act upon sodium ferrocyanide. 

The dehydrated ferrocyanide is first pulverized and then mixed 
with the powdered alkaline alloy. The grinding of these alloys is 
easy enough, because they are generally brittle. Ordinarily the 
grinding is done in the presence of a small quantity of mineral oil, 
the use of which prevents oxidation. 

The mixture is fused in furnaces at as low a red heat as possible. 
This fusion should, of course, be done out of contact with air. When 
the reaction is finished, there remains a fused mass consisting of 
cyanide as well as iron and spongy lead. 

These two foreign substances are separated from the cyanide by 
decantation or by filtration. The mass may likewise be treated 
with water, and after filtration the solution of cyanide may be evap- 
orated. The lead and the iron may also be separated. In order to 
do this, the mixture is melted on an inclined plane, when the lead, 
which is more fusible, runs off first, leaving the iron behind, or else 
the mixture is finely divided and stirred in a bath of melted lead, 
which retains the lead which was mixed with the iron, thus permit- 
ting the iron to be collected. This iron may then serve in the prepa- 


ration of ferrocyanides. The lead is itself used anew in the prepa- 
ration of the alkaline alloy. 

The proportion of ferrocyanide to alloy to be used depends on 
the quantity of alkali metal which the alloy contains. The authors 
claim that, in practice, an alloy containing 10% of alkali metal is 
the best adapted. It is, however, always better to use a somewhat 
larger quantity than is theoretically sufficient in the substitution 
of the alkali metal for the iron of the ferrocyanide. In practice, in 
order to prepare a double cyanide of sodium and potassium, 10 
parts by weight of the dehydrated potassium ferrocyanide and 13 
parts of the 10% lead-sodium alloy may be used. 

A modification of this process has been proposed by Hetherington, 
Hurter, and Muspratt (English patent March 20, 1894, March 1895) ; 
it consists in melting the alkaline alloy under a certain thickness of 
cyanide obtained in a previous operation, and adding to this mix- 
ture, in small portions, the dried ferrocyanide. These inventors 
recommend using an alloy with 13% sodium. When the reaction is 
complete the final product is found in three separate layers melted 
lead, reduced iron, and alkalicyanide, which are easy of separation. 
The lead-sodium alloy may be replaced by the lead-potassium alloy, 
but the former is preferable. 

Does the use of alkaline alloys possess, as stated by the inventors 
of various patents on this subject, a distinct advantage over the 
use of alkali metals alone? This question is not so easily answered. 
It cannot be denied, in view of the ease with which the alloys are 
obtained, that the potassium-lead alloys, and more especially the 
sodium-lead alloys, are much cheaper, all things being equal other- 
wise, than the same alkali metals themselves. From this point of 
view the processes of Vautin and Hetherington would possess ad- 
vantages. But, on the other hand, one has a right to ask, What is 
the role played by the lead in these reactions? It is known that 
lead has but a slight affinity for the cyanides, and that is the reason 
why lead cyanide has never been prepared. 

The use of alkali cyanides has even been praised as a means of 
reducing lead carbonate to the metallic state. It becomes evident, 
therefore, that in the action of lead-sodium alloy on alkali ferrocya- 
nide, sodium alone enters into the reaction. 

Since the content of the alkali metal in the alloys is generally 


about 13%, in order to produce the same result as 100 parts of so- 
dium one must use 770 parts of the lead-sodium alloy. Therefore the 
net cost of lead-sodium alloys containing 13% sodium should be 7.7 
times less than that of metallic sodium, in order that such processes 
as those of Vautin and of Hetherington, etc., may possess pecu- 
niary advantages over those processes represented by Rossler-Hass- 
lacher, etc. The cost of the alloy must, indeed, be even cheaper, 
because in the first processes one must also reckon the expenses due 
to the separation of the iron and the lead in order to recover the 
latter. Now then, according to data on this subject, the price of 
lead-sodium alloys containing 12-15% sodium is not so low, in 
fact it is only one fifth of the price of metallic sodium, the price of 
sodium taken into account being that made especially to manufac- 
turers of cyanides. 

It would seem, moreover, that the advantage in using alkali 
alloys is rather in the case of working and manipulating the prod- 
ucts. In this case, one must assume that the lead is either a reduc- 
ing agent preventing the formation of cyanates, or simply a diluting 
agent (when it is considered that it forms 87% of the alloy) whose 
r61e would be to prevent the sodium from floating on top of the mass 
of melted ferrocyanide and thus not enter the reaction. 

In these two cases the advantage offered by the alkali alloys 
would be especially valuable from the point of view of the yield in 

Dalinot's Process. This also depends on the action of an alkali 
metal on ferrocyanide, but in this case the metal is no longer used 
in the free state; it is produced in the nascent state during the 

In a suitable vessel, and at the required temperature, place 
dried ferrocyanide mixed with sodium hydroxide or with potas- 
sium hydroxide in as dry a state as possible. To this mixture add 
finely pulverized calcium carbide. The ingredients should be 
added in atomic proportions. 

As is well known, calcium carbide possesses remarkable reducing 
properties. Under the conditions just mentioned it acts upon 
the only body containing oxygen, that is the alkali, and sets the 
metal free. 

This reaction is the result of the well-known fact that sodium 


unites with oxygen, producing NaO + 100 calories, while calcium 
combines with oxygen, forming CaO + 135 calories. Consequently 
the calcium removes the oxygen from the sodium hydroxide, leaving 
lime and metallic sodium. 

The sodium is found in the mass in the molecular state. It 
comes in contact with the cyanogen which was united to the iron, 
and which has been set free in consequence of the ignition of the 

In accordance with the law that the most stable body is the 
one first formed, sodium cyanide is produced, the reaction being 

FeCy 6 K 4 +Na 2 0+C 2 Ca 

= 4KCy + 2NaCy + CaO + Fe + various carbides. 

During the operation an energetic stirring of the fused mass is- 
maintained so as to have perfect contact. When the operation is 
over, the fused mass is filtered through a hot filter in order to sepa- 
rate the residue of iron and lime. 

Instead of the caustic alkalis, the alkali carbonates may like- 
wise be used. 

The calcium carbides should be quite dry. For this purpose 
it is ground in a grinder whose interior is perfectly sheltered from 
the atmosphere, and is in air-tight communication with a reservoir 
containing sulphuric acid. This procedure does not lack in origi- 
nality, but its working does not seem to be very practical. It is 
quite difficult, in fact, to obtain an alkali completely free of water,. 
whence comes a loss in cyanide compounds under the form of ammo- 
nia. On the other hand, calcium carbide of commerce is frequently 
impure and gives to the cyanide a more or less intense coloration,. 
injuring the commercial value of this product. 

Adler's Process. This process was patented in July, 1900, and is: 
but an improvement on that of Liebig. With the object of reducing 
the cyanates, Adler no longer employs charcoal but alkali ferro- 
cyanides according to the reaction: 

(1) FeCy 6 K 4 +C0 3 K 2 = 4KCy+2KCyO+CO+Fe. 

(2) 2KCyO + 2FeCy 6 K 4 = lOKCy + 2FeO + 4C + 4N. 

(3) 2FeO+2C = 2CO+2Fe. 


368 parts of dry ferrocyanide of potassium are fused with 138 
parts of dry potassium carbonate, and toward the end of the reac- 
tion 736 parts of dry ferrocyanide are added a little at a time. An 
abundant froth produced by the reaction of the cyanate is at first 

When the mass is in a tranquil fusion, it is filtered in order to 
separate the cyanide formed from the impurities iron, oxide of 
iron, etc. 

Etard's Process. This process is connected rather with the 
extraction of cyanides from sulphocyanides, since it consists in 
removing the sulphur of the sulphocyanides by means of the iron 
of the ferrocyanides according to the reaction 

Fe(CN) 6 K 4 +CNSK = FeS+5CNR4-C 2 N 2 . 

In practice the perfectly dry ferrocyanide is fused with the 
equally dry sulphocyanide. Sulphide of iron is formed, which 
is deposited during quiet fusion. The cyanide formed is decanted 
hot; the cyanide gas which is set free is not lost, but collected in 
an alkaline solution. The mass may likewise be taken up by water, 
methyl alcohol, or ethyl alcohol. In the first case, work is carried 
on as rapidly as possible out of contact with air, in order to avoid 
the formation anew of the ferrocyanides. In order to avoid the 
formation of the cyanide gases and consequently to increase the 
yield, carbonate of potassium may be added to the mixture of ferro- 
cyanide and sulphocyanide. The reaction is then as follows: 

Fe(CN) 6 K 4 +CNKS+C0 3 K 2 =FeS + 7 

368 97 138 455 

In this wise, 7 molecules of cyanide of potassium are obtained 
instead of 5 molecules, as in the previous reaction. 

Bergmann's Process. This process, which is one of little prac- 
tical value, and which produces only the cyanides of copper and 
silver, is a wet method 

It consists in heating a solution of ferrocyanide in the presence 
of a copper or a silver salt, in sufficient quantity to effect the total 
union of the cyanide of the prussiate with the copper or the silver. 


The mixture should contain a certain proportion of free acid, 
which, producing the decomposition of the ferrocyanide, causes 
the formation of prussic acid, which unites with the silver or with 
the copper to form cyanides of these metals. 

In the case of the cyanide of silver the reaction is as follows: 

6N0 3 Ag + FeCy 6 K 4 = GCyAg + 4N0 3 K + (N0 3 ) 2 Fe. 

422 parts by weight of crystallized ferrocyanide of potassium 
are dissolved in 50 times its weight of water, to which is added a 
2% solution of 1020 parts of nitrate of silver. After slightly acidify- 
ing with sulphuric acid, the solution is brought to a^boil until the 
whole of the precipitate of ferrocyanide of silver which is first formed 
is completely transformed into cyanide of silver by absorbing the 
whole of the silver remaining in excess. This cyanide is separated 
by decantation and washings. 

In the case of the copper cyanide the reaction may be expressed 

6S0 4 Cu + FeCy 6 K 4 + 3S0 2 + 6H 2 

= 3CuCy 2 + 2S0 4 K 2 + S0 4 Fe + 6S0 4 H 2 . 

In order to avoid a too excessive action of the 6 molecules of 
free sulphuric acid which are formed in the course of the reaction 
it is well to operate in very dilute solution, or to neutralize the acid 
as fast as it is formed by the addition of alkali. Likewise a sul- 
phite may be used from the beginning. At first a reddish-brown 
precipitate of ferrocyanide of copper is formed, which under the 
action of heat is gradually transformed into a white, flucculent 
cyanide of copper. 

The cyanide of copper thus obtained furnishes very interesting 
double cyanides when digested in the cold with an alkaline sul- 


Sulphocyanides have but a very limited market. They consti- 
tute, as will be seen later, one of the most important residues in 
the manufacture of illuminating-gas. Moreover, for a certain time, 
they formed the basis of several methods of cyanide manufacture, 


due to the remarkable works of Caro, Conroy, and of Playfair, who 
demonstrated that they could be a profitable source of cyanide 

Thus, for a long time, attempts have been made to transform 
these salts into cyanides or into ferrocyanides, which find a more 
extended application. The interest taken in this subject is well 
shown by the numerous studies, and the various patents taken. 

Theoretically, this conversion of sulphocyanides into cyanides 
appears quite simple. If the formula of sulphocyanide of potassium 
is taken, for example, one sees that its conversion into cyanide is 
made by the simple removal of the atom of sulphur which it con- 
tains : 


There are two general methods which may be used in producing 
such a result. The first is one of reduction, in which case a sul- 
phide is formed 


The second, on the contrary, consists in removing the sulphur 
by oxidizing it with production of a sulphate: 

CNSK + R + 4 = S0 4 R + CNK. 


This method of treatment is the oldest, but it has never been 
used on an industrial scale. 

The first attempt along this line was made by Hadow, who used 
permanganate of potash and peroxides of lead and manganese. 
In a method for the determination of sulphocyanides by means 
of permanganates, Erlenmeyer showed that in an acid solution 
the reaction takes place quantitatively: 

5CNSK + 6Mn0 4 K + 4H 2 S0 4 = 5KCN + 6S0 4 Mn + 3S0 4 K 2 + 4H 2 0. 

This method is entirely demonstrated, but the high cost of per- 
manganate was a serious obstacle to its industrial application. Never- 
theless, this discovery of Erlenmeyer caused ' an awakening of 


ideas. Alt showed that in the presence of barium chloride, using 
HNOa as oxidizing agent, the reaction is likewise quantitative. 

The ingenious attempts of Parker and of Robinson (1888-1889) 
must also be mentioned. The latter made use of electrolysis. He 
passed the electric- current through a solution of sulphocyanide 
in sulphuric acid. Prussic acid, CNH, was formed, which was 
collected in an alkaline solution. The causes of failure of such 
processes may be easily understood. The prussic acid set free was 
a continual source of danger to the employes on account of its great 

Raschen's Methods. The next attempt was the use of nitric 
acid as oxidizing agent under certain fixed conditions. Such are 
the processes of Raschen and Brock, worked by The United Alkali 
Co., Limited. To the kindness of Dr. J. Raschen, Director of The 
United Alkali Co., Limited, we owe a complete description of his 
processes, which is reproduced in full. In the first of these processes 
the line of procedure, as indicated in the patents taken out by 
Brock and Raschen (1888, 1895, 1896), is as follows: A 20-30% 
solution of dry sodium or calcium sulphocyanide is used. A definite 
quantity of hot water, or, better still, of mother-liquor from a pre- 
vious operation, is placed in a hermetically closed boiler provided 
with a stirrer and the solution is heated to 96. The stirrer is then 
set in motion while at the same time the solution of sulphocyanide 
and nitric acid are added. The addition of these two solutions 
must be so regulated that there is always a slight excess of the acid in 
the mixture. The whole of the sulphur of the sulphocyanide is 
oxidized into sulphuric acid, while at the same time a mixture of 
nitrous acid, water-vapor, nitrogen , oxide carbonic acid, and hydro- 
cyanic acid is set free. These acids are passed through a scrubber 
containing water at 80 C., which absorbs the nitrous acid. After 
having undergone this first purification and having been cooled, 
the gaseous mixture passes into an absorption apparatus dividedin to 
two compartments. The first contains cold water, which absorbs a 
great portion of the hydrocyanic acid, allowing the carbonic acid 
and the nitrogen oxide to pass on; the second contains milk of 
lime, which retains the carbonic acid and the remainder of the 
hydrocyanic acid, so that at the outlet of the apparatus, nitrogen 
oxide escapes, which, mixed with air, is recovered under the form 


of nitric acid, capable of being used again in the same process. The 
solution of calcium cyanide in the second compartment is filtered 
from the precipitate of the carbonate of lime and converted into 
alkali cyanide by double decomposition. The solution of hydro- 
cyanic acid in the first compartment is neutralized by means of 
an alkaline solution, forming an alkali cyanide. The cold water of 
the first compartment may equally well be replaced by an alkaline 
solution. It is of the utmost importance that the operation be 
carried on absolutely out of contact with air, otherwise the nitrogen 
oxide, would become oxidized with the formation of nitrogen per- 
oxide, which latter would be absorbed by the alkaline solution, form- 
ing nitrite and nitrate, which would contaminate the cyanide and 
so be a serious hindrance to the fusion of this compound, the mix- 
ture of cyanide and nitrate reacting with violence. 

It is likewise necessary because of the extreme toxicity of the 
prussic acid to work very carefully and to maintain a slight vacuum 
in the apparatus, so that no gas shall escape into the air if the 
apparatus should leak. 

Raschen and Brock modified this process by using mineral oxi- 
dizing agents, such as the nitrates, chromates, peroxides of lead 
or of manganese in the presence of sulphuric acid. With the water 
is mixed the acid and the oxidizing agent and the whole brought to 
a boil; then is added, little by little, the sulphocyanide dissolved 
in water. It is necessary to use a somewhat larger quantity of 
oxidizing agent and acid than the theoretical amount indicated 
by the following reaction, using sulphocyanide of sodium as an 

CNSNa + 3S0 4 H 2 + 3Mn0 2 - CNH + S0 4 NaH + S0 4 3Mn + 2H 2 0. 

Toward the end a little more heat is applied in order to 
drive off completely the whole of the hydrocyanic acid. The 
gaseous mixture is collected and purified, as before. In the Wigg 
works at Runcorn, which belong to The United Alkali Co., Limited* 
this process slightly modified is in use at the present time on a 
large scale. 

Raschen and Brock have, in fact, found that better yields (96%- 
99% of theoretical) are obtained if more dilute solutions be used 
(170 grams per liter), and if the solution of sulphocyanide be poured 


slowly into the dilute and boiling nitric acid. At Runcorn sodium 
sulphocyanide is used, besides sodium nitrate and sulphuric acid, 
which latter act as oxidizing agent. 

The apparatus used in the decomposition consist of stoneware 
carboys A\, A 2 , A 3 , ... A n , placed in series, connected with each 
other by means of earthenware tubes starting at about mid-height 
of one carboy and .ending in the next at the bottom. Each one of 
them carries, besides, an outlet tube B and a tube C for the inlet 
of the steam, which latter tube serves as stirrer. 

First the carboys are filled with dilute sulphuric acid, then 
steam is let on so as to reach nearly the boiling-point. Then the 
solutions of sulphocyanide (170 grams per liter) and sodium nitrate 
are run in simultaneously. The letting in of steam and of solutions 
is so regulated that the temperature always remains constant, and 
the liquid passing from the first into the second carboy no longer 
contains traces of sulphocyanide, and the liquid of the last carboy 
is free from hydrocyanic acid. The gases which are liberated are 
chiefly hydrocyanic acid and nitrogen dioxide together with a little 
carbonic acid, nitrous acid, and considerable amounts of water- 
vapor. The gases pass first into the tower D, filled with quartz 

FIG. 2. Raschen's Apparatus. 

pebbles, through which they pass from bottom to top, where they 
meet a shower of cold water circulating in the opposite direction, 


which absorbs the oxides of nitrogen, without absorbing the hydro- 
cyanic acid, because the temperature has not been lowered. The 
water- vapor is condensed in an ordinary condenser E-, it carries 
with it a small quantity of hydrocyanic acid, which is neutralized 
with caustic soda. 

At their outlet the gas shows 75-80 F. They are conducted 
into the two cast-iron absorbers CiC 2 , which are cooled on the out- 
side and which contain caustic alkali. The hydrocyanic acid is 
absorbed, and the nitrogen dioxide is set free unaltered. This latter 
gas is brought in contact with air in order to recover the nitric acid, 
The recovery of this gas is done by passing the gas mixed with an 
excess of air through two towers of refractory stoneware M and N, 
which inclose quartz pebbles, and into which falls a shower of cold 

The amount of water and the volume of air used in the reaction 
should be carefully regulated in order to recover an acid of uniform 
concentration. However, it is necessary to have an excess of air 
over the theoretical quantity. This excess of air carries a part of 
the heat liberated by the oxidation of the nitrogen dioxide and 
serves as a refrigerating agent. The mixture of acid thus recovered, 
on coming out of the second tower is conducted directly into the 
first decomposition carboy, where it oxidizes a new quantity of sulpho- 

The whole circulation of the gases is made certain by Koerting 

The last operation is the evaporation of the cyanide solution in 
order to have a commercial product. This procedure is easily ac- 
complished in the laboratory, but quite difficult on an industrial 
scale. In fact the evaporation of large amounts of cyanide solu- 
tions always causes a more or less complete transformation of cyano- 
gen into ammonia. This loss is chiefly due to the action of super- 
heated steam in the cyanide mass. This objection may be easily 
removed by evaporating the solution in vacuo and by keeping 
it constantly stirred. The product obtained under these conditions 
is a white powder more or less agglomerate. It is free of sulphur 
and therefore particularly suitable in the extraction of gold. It 
contains, however, several impurities, due mainly to the caustic 
solutions used. T. T. Conroy, who has made a thorough study of 


Raschen's process,* states that the precautions taken in order to 
avoid any liberation of such toxic gases as hydrocyanic acid and 
nitrogen dioxide are perfect, and the total absence of any odor in 
the works is a convincing proof. 

Beringer's Process. Having studied thoroughly the conversion 
of sulphocyanides into cyanides by the oxidation process, Beringer 
discovered that the formation of carbonic acid was due to the pres- 
ence of free mineral acids, and thereupon conceived a process whose 
object is to carry on the reaction in such a manner as to form 
no free acid, or at least if any be formed, its effect is not 

In order to do this he uses nitric acid in sufficient quantity, 
but in the form of nitrate (of calcium or of barium). By causing 
a mineral acid, which is capable of setting free nitric acid from the 
nitrate, to act upon this salt ; the nitric acid will act on the sulpho- 
cyanide as an oxidizing agent; sulphuric acid will be formed at 
the same time as the oxidation is produced, but this acid will liber- 
ate a fresh quantity of nitric acid, which will oxidize more sulpho- 
cyanide, while the sulphuric acid formed will be held by the base 
of the sulphocyanide according to the reaction 

(CNS) 2 Ba + 2(N0 3 ) 2 Ba + S0 4 H 2 = 3S0 4 Ba + 2CNH + 4NO. 

In this way Beringer claims that the carbonic acid formed at 
the expense of hydrocyanic acid is reduced to a minimum, and that 
the yield of this latter is almost theoretical. 

The operation takes place in a hermetically closed receiver 
provided with stirrers. Into this receiver 32 kg. of barium nitrate 
and 700 liters of water are placed and the temperature brought to 
the boiling-point. Then are added slowly, either separately or 
mixed together in portions about equal, 37.2 kg. barium sulpho- 
cyanide and 31.6 kg. sulphuric acid of sp. gr. 1.84, to each of which 
100 liters of water have been added. 

The hydrocyanic acid liberated is carried away by the watery 
vapor and absorbed in suitable receptacles. 

* Jr. Soc. Chem. Ind., 1899, May 31. 



The oxidation processes have never been employed industrially 
to any great extent. Rauschen's methods only have enjoyed some 
interesting developments. They are in themselves rather danger- 
ous, for they all set prussic acid free, an excessively poisonous gas. 
Moreover, there is always fear of a later oxidations, the result of 
which would be a greater or less loss of cyanogen. 

The reduction processes are much more numerous, practical, and 
profitable, and at the same time free from danger. They are the 
only ones susceptible of being used in the industry of the cyanides 
obtained by the conversion of sulphocyanides. 

The various substances proposed for the accomplishment of 
the reduction are quite numerous: Hydrogen, carbon, hydro- 
carbons, various metals, etc. 

Playfair's Process. Playfair has thoroughly investigated along 
this line, and his remarkable researches have served as a basis for 
the reduction processes which are used at the present time. 

In one of his earlier investigations Playfair attempted to heat 
to redness a mixture of sulphocyanide of sodium or of potassium 
in a current .of hydrogen, based on the following reaction: 

4CNKS + 6H = K 2 S + 2CNK + 3H 2 S + 2C + 2N. 

He noticed an abundant liberation of hydrogen sulphide; after 
the reaction was completed there remained in the combustion-tube 
a mixture of sulphide and cyanide in almost equal proportions; 
from his data, only about 80% of the sulphocyanide was decom- 
posed. In the above equation, 110 parts of potassium sulphide 
corresponding to 130 parts potassium cyanide, the product of the 
reaction yielded 20% less cyanide than the theoretical amount. 
Besides, one half of the cyanogen is lost, as it is set free in the form 
of nitrogen, and the separation of the cyanide from the sulphide 
is not a very easy matter. This process was therefore quite imprac- 
ticable. Several years later Conroy repeated Playf air's experiments 
and confirmed every result. 

Next, Playfair tried the use of hydrocarbon vapors naphtha 
vapors for example as reducing agent. As in the preceding experi- 
ment he noted an abundant liberation of hydrogen sulphide, but at 
the end of the reaction he found no traces of cyanides. The residue 


was composed entirely of sulphides together with slight traces of 

When he heated sulphocyanide of sodium with charcoal, he 
obtained no better results. In this case he obtained traces only of 
cyanide and a considerable quantity of sulphide. 

Then Playfair tried the use of metals at first lead and zinc, for 
these only appeared suitable. The metals decomposed the sulpho- 
cyanide either in fusion or in solution according to the reaction 


After many experiments, Playfair adopted the following pro- 
cedure : 

He used a receiver made of black lead, whose form is that of 
an inverted muffle and which is provided with a tightly fitting lid. 
This apparatus is placed in a furnace in such a way that the top of 
the receiver extends 2 to 5 centimeters above the upper border of 
the furnace so that it becomes heated only at the bottom and the 
sides. Zinc is then melted in the presence of a small quantity of 
pulverized charcoal, which maintains a reducing atmosphere in 
the crucible. When the zinc is completely fused dry sulphocyanide 
is added, either cold or even in a melted state. The mass is kept 
stirred and the reaction continued till the mass becomes quite thick 
and begins to redden. At this point the reaction is complete. The 
mass is then allowed to cool, protected from the air. When cold, 
the mass is easily removed from the crucible, which does not appear 
at all attacked. The color of the mass should be pearly gray, if 
the reaction has been successful, in which case its solution will be 
entirely free of soluble sulphides. But if the mass has been super- 
heated, which happens especially when too large crucibles are used, 
it has a brownish and sometimes even a reddish color, and the solu- 
tion may contain as much as 15% of alkaline sulphide. 

As a rule one must assume a loss of about 5%, due partly to 
moisture and partly to the formation of small quantities of cyanate 
and carbonate. One should add also to the above loss that which 
may result from the formation of the double cyanide of zinc and 
potassium or sodium in consequence of a too high temperature, but 
this loss may be easily avoided by the use of a slight excess of sul- 


The melted mass is subjected to a systematic lixiviation in a 
series of vats. The alkaline cyanide solution is separated from the 
insoluble zinc sulphide by decantation. This latter substance con- 
stitutes about 65% of the fused mass. The solutions thus obtained 
vary considerably in concentration; that is, from 4 grams of sodium 
cyanide per liter to 220-240 grams. These latter solutions are 
evaporated in vacuum to the consistency of a thick paste, which 
on cooling crystallize. The following is an analysis, made by 
Playfair, of one of these solutions. The figures represent the 
amounts per 100 cc. of solution to be evaporated. 

Sodium cyanide 22.00 gm. 

Cyanate 3.06 

Double cyanide of zinc and sodium 1 . 55 

Sodium carbonate 0. 71 

Sodium sulphocyanide 1 . 80 

The following is an analysis, made by Playfair, of the concen- 
trated product : 

Water 26.00% 

Cyanide of sodium 54. 70 

Cyanate of sodium (contains formate) 9.45 

Double cyanide of zinc and sodium 3.90 

Sulphocyanide of sodium 4 . 30 

Carbonate of sodium 1 . 65 

Playf air's process marks a real progress; it can be applied in- 
dustrially, since, according to the inventor, the yield is about 70% 
of the theoretical amount. This result is obtained if care be taken 
to concentrate the solutions in a vacuum of 66 centimeters, using 
solutions containing at least 22% of cyanide, so as to avoid loss of 

Dr. Hans Luttke's Process. This process is based on the same 
principle. It consists in melting sulphocyanide with zinc powder. 
In an iron crucible are fused together 

97 kg. sulphocyanide of potassium, 
65 " zinc powder. 


The mass is stirred while being heated, and from the moment it 
fuses, the crucible is removed from the fire. The reaction then goes 
on by itself. 

When the fused mass is treated with water it yields about 60 kg, 
of cyanide, i.e., 90% of the theoretical amount. The sulphide of 
zinc which is obtained as a by-product may be profitably used as a 
mineral color. 

The reaction takes place between 360 and 400; this temperature 
may be lowered by an addition of 1% to 2% caustic alkali, which 
at the same time, increases the yield of cyanide. 

Various other metals have been tried. Lead, which was also 
recommended by Playfair, has the advantage of not forming double 
cyanide of lead and potassium, but on account of its high atomic 
weight, three times as much lead as zinc are required to perform 
the same work, while, at the same time, it has a tendency of falling 
to the bottom of the crucible without remaining mixed with the 

The reduction of sulphocyanide may be well carried on with the 
use of tin, but tin sulphide dissolves in rather appreciable quanti- 
ties in the alkaline cyanide. 

The use of copper is no more successful, for it gives rise to cupro- 

Process of the British Cyanide Company. Notwithstanding the 
foregoing, this company has quite recently patented a process in 
which copper is used. This process is based on the fact that when 
metallic cyanide compounds are heated in a current of hydrogen at 
a suitable temperature, they set free the whole of their cyanogen in 
the form of hydrocyanic acid, which may be absorbed by alkaline 
solutions. The British Cyanides Company, Limited, noticed that the 
salt which is the best adapted for this reaction is sulphocyanide of 
copper. This salt, which is first thoroughly dried, is placed in a 
receiver provided with a stirrer and mixed with finely divided copper 
in considerable excess (equal quantities of sulphocyanide and of 
copper). Perfectly dry hydrogen is passed through the apparatus, 
in order to expel the air and then it is heated to 150 C., and grad- 
ually to 350 C. 

When the reaction is almost complete, the temperature is raised 


to 500 C. ; the current of hydrogen being constantly kept, up. The 
reaction is as follows: 

(CNS) 2 Cu 2 + 2Cu + H 2 = 2Cu 2 S + 2CNH. 

The gas which is liberated is a mixture of hydrocyanic acid with 
hydrogen in excess. It is conducted through a strong alkaline 
solution which absorbs the hydrocyanic acid. The excess of hydro- 
gen may then be collected and used anew. The cuprous sulphide 
remaining behind may be treated in order to recover the copper 
or copper salts. In place of hydrogen may be used coal-gas or 
water-gas provided they be free from carbonic acid, oxygen, and 

Conroy tried using copper and zinc simultaneously, or copper 
with lead-sodium alloy, but in neither case was he able to obtain 
a pure product. 

The results obtained with iron were quite satisfactory. In his 
patent, No. 21,451, obtained in 1893, Conroy recommends treating 
the dry sulp ocyanide with finely divided reduced iron, pitch, and 
a, small amount of charcoal in order to prevent oxidation. The 
reaction takes place at about 400, but, as Conroy himself noticed 
it is quite irregular, and the yield may be, in consequence, quite 
variable. Moreover, it is rather difficult to ascertain exactly the 
end of the reaction, and if the operation be carried on too far, reac- 
tions may take place which are quite opposed to those desired. 

Hetherington and Musspratt's Process. This process (English 
patent 5830, 1894) is based on this principle: It consists in heat- 
ing iron filings or turnings with tar in order to reduce the oxide 
coating to the metallic state. The iron thus treated is mixed in 
the proportion of 70 to 80 parts with 20 to 40 parts tar and 100 
parts alkaline sulphocyanide. This mixture is heated to 350 C., 
thereabouts, in a closed vessel connected by means of a tube with 
a retort, where the volatilized sulphocyanide is condensed. The 
resulting product is iron sulphide, a tar-like residue, and alkaline 
ferrocyanide. It is treated with hot water, and the filtered solu- 
tion is subjected to the action of a current of carbonic acid, which 
displaces the hydrogen sulphide, after which the solution is con- 
centrated to crystallization. 


Process of the Silesia Verein Chemische Fabrik. This process is 
in all points about the same as the foregoing. The sulphocyanide 
is first melted, then poured upon reduced iron filings, turnings, or 
shavings, and then heated to dull redness. For this purpose 1 kg. 
of iron may be profitably used for each kilogram of crystallized 

If the sulphocyanide be in solution, this is concentrated, and 
iron shavings added in sufficient quantity to form a pasty mass. 
This is then transferred to receivers of moderate dimensions 
which can be transported and heated at a temperature not above 
800. In order to complete the decomposition properly, incan- 
descent bodies, such as pieces of iron, charcoal, and highly heated 
stones, are thrown on the mass. Then the receiver is removed from 
the fire and allowed to cool. 

In each case the product is treated either with water, in order 
to obtain ferrocyanide, or with alcohol, in order to obtain cyanide. 

Goerlich and Wichmann's Process. This process differs but 
little. It consists in fusing the sulphocyanide with iron, passing 
a moist current of air charged with carbonic acid through the fused 
mass and then treating it with water according to the reaction 

2K 6 Cy 6 6FeS 4- 170 + 21H 2 + 2C0 2 

= 2K 4 FeCy 6 3H 2 + 2C0 8 K 2 + 5Fe 2 (OH) 6 + 2S 

At the present time the transformation of sulphocyanides into 
cyanides is preferably done in the wet way. 

These processes originated with the patents taken out by Pitt 
and Bower, the object of which was the recovery of the cyanide 
compounds occurring in gas-liquor. 

Bower's Process. In Bower's first process these gas-liquors are 
treated with addition of metallic iron or ferric salt in sufficient 
quantity to convert the whole of the cyanide compounds into ferro- 
cyanide and iron sulphocyanide. After distilling off the ammonia 
in the presence of lime, the residual liquors containing the sulpho- 
cyanide and ferrocyanide of calcium are treated with an acid solu- 
tion of cuprous chloride, which precipitates the cyanide compounds 
as insoluble cuprous salt. While this precipitate is still moist, it 
is treated with finely divided iron in order to convert it into soluble 


iron sulphocyanide and insoluble iron ferrocyanide. At the same 
time metallic copper is formed. The ferrocyanide of iron, which 
is separated by filtration, is treated with a strong alkaline solu- 
tion in order to obtain an alkali ferrocyanide. The solution of iron 
sulphocyanide is evaporated. 

Later Bower noted that when the decomposition of copper 
sulphocyanide is brought about by the use of iron at a high tem- 
perature and under pressure, the copper which is set free reacts 
with the sulphur of the iron sulphocyanide and forms copper sul- 
phide and iron ferrocyanide. Bower immediately obtained a new 
patent, according to which the iron sulphocyanide obtained as 
before stated is treated with metallic copper in an autoclave and 
at a high temperature under pressure. 

The reaction follows: 

3(CNS) 2 Fe + 6Cu = Fe(CN) 2 2Fe(CN) 2 + 6CuS. 

The precipitate obtained is afterward treated with an alkaline or 
alkaline-earth solution giving a soluble ferrocyanide. 

Conroy's Process. Taking up Bower's work, Conroy thought of 
substituting another and less expensive metal for copper, and chose 
iron. He noted that if a solution of iron sulphocyanide be boiled 
under pressure with metallic iron there will be formed at 

Undecomposed F |de 



115-125 (after heating 13 hours). 62.0% 36.8% 

150-165 " " 4 " 10.6% 88.0% 

190-200 . " " 2J " 9.2% 90.5% 

Having settled this important point, Conroy sought to obtain 
a similar result with potassium sulphocyanide or other impure 

His first experiment along this line was with a mixture of 
potassium sulphocyanide with a soluble iron salt. The results were 
as follows: 

Non-decomposed Ferrocyanide 
Sulphocyanide. Obtained. 

At 160 with 1 hour's heating 38.0% 52. 6% 

At 160 " 2 hours' " 22.0% 67.5% 

At 150-160 with 5J hours' heating 95.0% 


The result being favorable,' Conroy determined to apply this 
method on an industrial scale, and in order to do this he undertook, 
in company with Hawliczek and Clayton, experiments bearing upon 
calcium sulphocyanide, the important industrial waste product in 
the, manufacture of gas. 

In a cast-iron cylindrical autoclave provided with a stirrer turn- 
ing at the rate of 40 revolutions per minute a mixture of (1) a solu- 
tion of calcium sulphocyanide, 400 g. per liter; (2) a solution of 
ferrous chloride, 250 gm. per liter and an excess of iron filings or 
shavings is heated to 135-140 C. and under a pressure of 50-60 
pounds per square inch. Under these conditions he observed that 
the time of the decomposition of the sulphocyanide that it varies 
with the amount and fineness of the iron used, according to the 
following table 

Iron in Excess of Sulphocyanide Time of 

Theoretical Amt. Decomposed. Reaction. 

12 hours 

Si " 

Si ". 

According to Conroy the reaction is as follows: 

2CNSK+FeCl 2 +2Fe = 2KCl+Fe(CN) 2 +2FeS. 

The mixture of sulphide and of ferrocyanide of iron is then 
treated with a strong alkaline solution, there being formed soluble 
alkali ferrocyanide, while the sulphide of iron undecomposed re- 
mains insoluble: 

3(CN) 2 Fe+4KOH+H 2 + = Fe(CN) 6 K 4 +Fe 2 (OH) 6 . 

But this treatment requires a large excess of alkali, and moreover 
there is an appreciable loss of this compound varying from 12%-28%. 
It is better to replace it by treatment with hydrochloric acid. In 
fact, if the mixture be treated with this acid the sulphide of iron 
goes into solution, while a pale-blue precipitate is formed which is 
insoluble in hot potassium carbonate, but which yields potassium 
ferrocyanide under the action of a current of air. 

This method presents, moreover, the great advantage of giving 
ferrous chloride, which may thus be used in the reaction 

3(CN) 2 Fe+6KCl+FeS = Fe(CN) 6 K 4 +3FeCl 2 +K 2 S. 

Iron shavings 
Reduced iron 

8 times 
J5.55 " 
[1.70 " 



All these processes yield ferrocyanide, which product must then 
be reduced to cyanide. They therefore do not solve the problem 
completely, which is the production of the cyanide direct. 

Raschen, Davidson, and Brock's Process. Nevertheless there 
exist special processes which fulfill this purpose, among them may 
be cited that of Raschen, Davidson, and Brock (1894). It is based 
on the conversion of sulphocyanides into cyanides by ignition in the 
presence of an excess of alkali or of alkaline earth, together with 
charcoal or a hydrocarbon. The sulphocyanide used in this case 
is produced by the action of carbonic acid on a mixture of milk of 
lime, sulphide of carbon, and ammonia heated in a closed vessel. 
The resulting product is treated with an alkaline carbonate filtered 
and evaporated to dryness. Quicklime is added to the crude sulpho- 
cyanide together with a mixture of powdered charcoal, resin, tar, 
or any other such substance. The whole mass is heated as rapidly 
as possible to a bright-redness in a vessel provided with a 

The mass is then allowed to cool, avoiding as far as possible the 
access of air, and then it is washed with water. In this way is 
obtained a solution of alkali cyanide containing a small amount of 
calcium sulphide, which latter product may be gotten rid of by well- 
known methods. 

Theoretically, this process seems very simple and reasonable, 
but unfortunately no data could be obtained concerning the yields 
which it furnishes and concerning its industrial application. 

Etard's Process. This process, which has already been mentioned 
(Chapter I, 1) and which consists in treating the alkali sulpho- 
cyanide with the ferrocryanide of the same metal either alone or 
mixed with a carbonate, has not, to our knowledge, been industri- 
ally applied. 

Finlay's Process. Finally may be mentioned the original process, 
patented in Germany by Finlay (patent 8604, 1896). It consists 
in producing simultaneously sulphocyanide and alkali cyanide 
by igniting at 1000 a mixture of alkali or of alkaline earth with 
charcoal in an atmosphere free from oxygen and consisting chiefly 
of nitrogen and sulphuric anhydride. Through the solution of the 
mixture thus produced a current of nitrogen and carbonic acid, in 
the presence of an oxidizing agent, is passed. Hydrocyanic acid 


is removed and passes into an alkaline solution, forming an alkali 

Finlay recommends the following: 

A mixture of equal parts of charcoal and caustic or carbonated 
alkali, especially barium carbonate, is heated to about 1000. A 
mixture of nitrogen and sulphur dioxide obtained by direct com- 
bustion of sulphur in air is transmitted upon the incandescent mass. 
Under these conditions there is produced a mixture of cyanide and 
sulphocyanide of barium. When this reaction is complete, the mass 
is allowed to cool and is taken up with water. After a suitable 
addition of an oxidizing agent (of the nature and use of which Finlay 
gives no information) a mixture of nitrogen and carbonic acid ob- 
tained by the combustion of charcoal in a current of air is trans- 
mitted into this boiling solution. The barium separates out as an 
insoluble carbonate, while the hydrocyanic acid which is displaced 
is carried off by the gaseous current. The hydrocyanic acid is con- 
densed in a cooler kept at a temperature of 4-5 C. and combined 
with a caustic alkali. At the same time the sulphocyanide is de- 
composed into hydrocyanic acid and sulphur dioxide. This latter, 
carried off by the nitrogen, regenerates thus the initial mixture of 
gas used for the production of cyanide and sulphocyanide. 

On account of its originality, this process deserves some atten- 
tion, but unfortunately it is quite probable that the liberation of 
hydrocyanic acid will check its industrial development, as is the 
case in all those processes where such a liberation takes place. 


It is the custom to designate under " synthetic or direct proc- 
esses/' all those processes the essential principle of which consists 
in uniting by means of any energy the three fundamental bodies 
entering into the composition of cyanides carbon, nitrogen, and 
alkali metal these three bodies capable of being either in a free or 
nascent state or in a combined state. 

The. indirect processes which have just been reviewed have been 
able to supply the needs of the trade at a time when the use of cya- 
nides was very limited, but soon the requirements of industry made 
necessary simpler, less defective, and less expensive processes. 


Nitrogenous organic substances, which for a long time have 
been the raw materials of this industry, have in general a very high 
value relatively, because of their extensive use either in human 
or animal nutrition, or in agriculture, or in other industries. There- 
fore they could not be economically used for a preparation which 
utilizes only their carbon and nitrogen. 

It is consequently necessary, if it is desired to work under really 
economic conditions, to make use of waste or refuse products, which 
are necessarily insufficient, especially from the point of view of 
the percentage of useful products which they contain. 

The percentage of nitrogen in these substances is especially 
small in comparison with that of carbon; therefore it is always 
necessary to ignite them beforehand, in order to obtain a much 
richer nitrogenous charcoal. In this preliminary operation f 
of the nitrogen is lost under the form of ammonia. This loss is 
unfortunately not the only one, and at the time of the forming of 
the cyanide with the nitrogenous charcoal f and even f- of that 
remaining is lost, so that finally only J or ^ of the total nitrogen 
is utilized. 

If to these losses in nitrogen be added those not less important, 
occasioned by poor yield, from the point of view of the alkali car- 
bonate used, and those produced by the volatilization of the cyanide 
at the temperature at which it is necessary to work, it is easy to 
see that such processes are far from giving satisfactory results or 
being economical, notwithstanding the remarkable improvements 
which they have undergone. 

It is therefore quite natural to have sought to produce cyanides 
by the synthetic or direct way, which, besides the advantage it 
possesses of producing the product desired directly, allows this 
product to be obtained much cheaper and in a state of greater 
purity. Of the three substances which, in general, constitute the 
cyanides, carbon occurs wide-spread, is easily found, and very cheap ; 
the alkali metals are likewise widely distributed. As to the nitro- 
gen, although it occurs distributed in extensive amounts on the 
surface of the globe, it is quite difficult to produce in a free state. 

Constituting four fifths of the atmosphere which surrounds us, it is 
quite natural to think of utilizing the nitrogen, either in the form 
of air or in the free state extracted from the air. The idea of using 


the atmospheric air in the manufacture of cyanides is not new. 
It proceeds from a series of observations made by many investi- 

In 1828 a chemist of Besanon, named Desfosses, repeating 
the old experiments of Scheele and Curandeau, remarked that the 
nitrogen unites with carbon in order to form cyanogen when a 
current of this gas or of air passes over a mixture of charcoal and 
carbonate of potash at a red heat. 

In 1835 Dawes discovered the existence of cyanide of potassium 
in the molten masses which are formed in the furnaces for the smelt- 
ing of iron. 

In 1837 the English investigator Clark made the same discovery. 
In examining an efflorescence which was produced at the orifice of 
some blast-furnaces on the Clyde, he noticed that it was made up 
almost entirely of potassium cyanide. 

In the same year, having established hot-air bellows in blast- 
furnaces, Neilson likewise observed the formation of masses which 
contained up to 43% potassium cyanide. 

These were confirmed by other observations, notably in the 
Harz, at Magdesprung, and at Zuicken by Bromeis in 1842. In 
1843 Redtenbacher proved a similar phenomenon in the furnaces 
at Mariazell in Styria, where the production of potassium cyanide 
thereby became industrially important. 

Moreover, in 1839 Lewis Thompson demonstrated that if a 
mixture of coke, potassium carbonate, and iron filings be heated 
at a high temperature and a current of air be passed over the mass, 
there will be formed potassium cyanide the yield of which will be 
greater than that obtained by not using air even when animal 
charcoal rich in nitrogen be used. On account of this remarkable 
investigation the Society of Arts bestowed a gold medal on Lewis 

In 1841 Fowner, and likewise Young, confirmed this result. 

But other chemists, and particularly Erdmann and Marchand in 
1841, and Wohler somewhat later, disputed their assertions, and 
claimed that the cyanide formed was due entirely to the nitrogen 
of the coal and that the reaction would not take place with dry 

In 1845 the question of the formation of cyanide in the blast- 


furnaces being studied more thoroughly, Bunsen and Playfair were 
able to show that this product is formed in the zone situated exactly 
above the blast-pipes through which hot air was being blown. They 
experimented on this subject with the result that it received scien- 
tific and industrial sanction and exerted a considerable influence 
on the ideas concerning the role played by nitrogen. By making 
an opening in the wall of a blast-furnace of the iron- works at Alfreton, 
exactly above the orifice of the blast-pipes, they noted the formation 
of an abundant sublimation of potassium cyanide, which, according 
to their calculation, might react 188 kg. in 24 hours. From this 
experiment they drew the conclusion that the cyanide formed was 
due solely to the atmospheric nitrogen, and not to that chemically 
combined with the coal. Moreover, they established clearly the proba- 
bility of this theory by another experiment. 

In passing air through a tube containnig a mixture of 1 part 
sugar charcoal and 2 parts of perfectly pure carbonate of potash, 
heated to a temperature high enough to cause the reduction of the 
alkali carbonate, they obtained an abundant formation of potassium 

In 1851 Riecken confirmed in all points the data presented 
by Bunsen. This investigator showed without any doubt that 
cyanogen may be formed in the absence of every other source of 
nitrogen except that of atmospheric air, provided that the latter be 
previously heated and transmitted in the form of a continuous current, 
and that the reaction be carried on at a temperature sufficiently 
high to reduce the potassium compounds employed to the metallic 

Some time later Delbruck's new experiments removed all doubt 
from the works of Bunsen and Riecken. 

These first principles being admitted, it was immediately planned 
to make it the basis of a process for the manufacture of cyanide on 
an industrial scale. 

The first practical application undertaken along this line was 
in 1843. This was made by Possoz and Boissiere, at first in 
their works at Grenelle, and the next year at Newcastle, under the 
direction of an English company. This process was based on the 
fact demonstrated by Desfosses in 1841, that if a current of nitrogen 
be passed over a mixture of charcoal and potassium carbonate 


heated to redness, there is formation of potassium cyanide. Not- 
withstanding unheard-of efforts, great sacrifices, and several years 
of struggle and in spite of their rare perseverance, the two 
French chemists could not hold out against competition, and were 
forced to abandon the exploitation of their process. That was 
because the yield of cyanide was small, and consequently the net 
cost was greatly increased. 

Numerous attempts followed that of Possoz and Boissiere, and 
among them may be c ted : 

In England, those of Newton in 1843, Swindel in 1844, Blairs 
and Bromwell in 1847. 

In Germany, those of Welden in 1879, and Alder in 1881. 

In America, those of Mond in 1882, Fogarty in 1883 and 1887, 
and Dickson in 1887. 

And, finally, in France, those of Ertel in 1846, Armengaud in 
1847, and Margueritte and Sourdeval in 1862. 

All these processes are based on the action of atmospheric air 
on a mixture of charcoal and an oxide or carbonate of an alkali 
heated to a very high temperature. 

The results obtained by these various manufacturers, however 
encouraging they may have been, were nevertheless far from being 
satisfactory. Therefore these processes had a very short existence. 

The quantities of cyanides produced were, in fact, very small, 
and the net cost was consequently very great. If to this great 
objection be added that none the less serious of the rapid wear and 
tear of apparatus brought about by the extremely high temperature 
necessary for producing the reaction, the causes of the failure of 
these attempts will be readily understood. 

The attempt was made to overcome the difficulty by utilizing 
nitrogen in another form, and for this purpose ammonia-gas was 
suggested. This gas in fact, besides being relatively cheap, is 
14 /i 7 of its weight in the form of nitrogen, and it has a greater chem- 
ical affinity than that of nitrogen. In fact it was proved by the 
experiments of Langlois and Kuhlmann that if dry ammonia- 
gas be passed over charcoal heated to redness there will be formed 
ammonium cyanide according to the reaction 

4NH 3 + 3C = 2NH 4 CN + CH 4 . 


This was not, indeed, a new idea. Brunnquell, later Karmrodt, 
and finally Lucas had already tried to utilize the ammonia produced 
in the ignition of nitrogenous organic matters, and which forms 
part of the volatile products arising from this decomposition. 
Toward this end these products were made to pass through retorts 
or cylinders charged with charcoal impregnated with potash; but 
notwithstanding certain advantages these processes never received 
industrial sanction. 

Laming, in 1843 and 1845, made this idea the basis of two processes 
for the manufacture of cyanides. But these attempts were like- 
wise futile. Other manufacturers and investigators studied- this 
question also, their results often being contradictory and their experi- 
ments were never taken up outside the laboratory. 

The weak points of the experiments undertaken along this line 
are (1) the difficulty of manipulating such a volatile gas as am- 
monia, (2) the necessity of producing a very high temperature, 
(3) the considerable loss due to volatilization, and (4) the rapid 
deterioration of the apparatus. 

To the above should likewise be added the fact that at such 
high temperatures ammonia-gas begins to undergo an appreciable 
decomposition, which, of course, is lost to the reaction. 

Another very ingenious solution of the problem had been pro- 
posed by Gelis, and was taken up about 25 years ago by Tcherniac 
and Gunzburg. It consisted in producing cyanides through the 
intermediary of sulphocyanides, formed by the action of ammonia 
on the sulphide of carbon. 

During the last few years this question has again become the 
object of numerous and important researches, but along other lines, 
and which permits the discovery of a real synthetic process to be 
foreseen in the near future, a process at once practical and of in- 
dustrial value. 

These processes are based on the action of nitrogen or of am- 
monia upon the alkali metals or their carbides. 

The reaction of ammonia oh the alkali metals was shown a long 
while ago by Gay-Lussac and Thenard. 

It is, in fact, known that if perfectly dry ammonia-gas be passed 
over potassium or sodium at a suitable temperature (not very high) 
a clearly defined compound, an alkali amide, is obtained which in 


contact with charcoal under suitable condition forms alkali cyanide. 
The low price and the facility with which large quantities of alkali 
metals are prepared leads to the belief that processes based upon 
this reaction will be put to practical use. It is evident that in this 
case it is no longer necessary to produce the extreme temperature 
required for the reaction of alkaline compounds formerly used, and 
from this fact losses through volatilization will be avoided while 
decreasing the wear and tear of the apparatus. 

On the other hand, it is to-day clearly proven that carbides are 
capable of fixing nitrogen, and, under certain conditions, of forming 

These two important observations have formed the basis of 
numerous patents recently granted, especially in Germany. The 
experiments seem to be successful, and in the near future the solu- 
tion of this question may be met. 

The solution would all the more be hastened through the dis- 
covery of a practical and economical process of fixing the nitrogen 
of the air, a question which has likewise made considerable progress, 
and all the more through the synthetic production of ammonia by 
the aid of this same nitrogen. 

Whenever this problem is solved, that of the manufacture of 
cyanides will be near its solution. 

The synthetic processes put into operation may be divided into 
two large classes: 

(1) Processes using atmospheric nitrogen. 

(2) Processes using ammoniacal nitrogen. 

Some of these processes are capable of using either atmospheric 
nitrogen or the nitrogen of ammonia. Such processes will only be 
mentioned in the first class, but will be discussed among those 
processes which are based on the use of ammonia. 


The discovery of potassium cyanide in blast-furnaces, and the 
remarkable investigations of Bunsen, Playfair, Riecken, and of Del- 
bruck, which fixed in an irrefutable manner the remarkable role 
played by atmospheric nitrogen in this formation, had the happy 


result of inciting manufacturers and investigators to utilize atmos- 
pheric air, or the nitrogen contained therein for the manufacture of 
cyanide compounds. 

As is well known, the atmosphere is composed of a mixture of 
oxygen and nitrogen, contaminated more or less, according to 
circumstances, with water, carbonic acid, ammonia, etc. In reality 
nitrogen forms about four fifths of the air, since air is composed of 
21% oxygen and 79% nitrogen by volume, or 23% and 77% by 
weight. Air therefore is an inexhaustible and profitable source 
of nitrogen for the manufacture of cyanides. 

At first it was attempted to use the atmospheric air, but the 
presence of the oxygen interfered considerably with the reactions. 
That is the reason why the attempt was made to use the nitrogen 
from which the oxygen had previously been removed. 

The separation o these two gases is not such an easy task as one 
would be led to believe, and several methods have been devised for 
this purpose. Therefore it may not be out of place, before taking 
up the study of processes for the manufacture of cyanides by the 
use of nitrogen of the air, to first pass in review the various means 
employed for the separation of these two principal constituents of 
air, oxygen, and nitrogen. 

These methods almost all depend on the following principle: 
If a current of air be passed over an easily oxidizable substance 
tinder suitable conditions, this substance will absorb the oxygen 
and leave the nitrogen free and pure. 

Most oi the metals, and even certain metalloids e.g., phosphorus 
or charcoal may be used for this purpose. 

As a rule, whenever it is desired to obtain almost chemically pure 
nitrogen, copper or iron is used. 

A current of air is passed over copper heated to redness, which 
absorbs the oxygen with formation of oxide of copper, while the 
nitrogen is left almost pure. Often passing the gas only once 
over the metal is not enough for the total absorption of the 
oxygen. This is an objection which may be easily .remedied, and 
thus a gas absolutely free from oxygen obtained. This operation 
being carried on at a high temperature, the resulting gases are like- 
wise hot, which fact may be of great use in certain processes. 

Lupton has modified this pr cess in such a way that a better 


yield of nitrogen is obtained, and the process is carried on con- 

His process consists in passing air through an aqueous solution 
of ammonia before passing it over the copper; the ammonia carried 
away by displacement then passes over the oxide of copper formed 
and reduces it to metallic copper according to the reaction 
3CuO+2NH 3 = 3Cu + 3H 2 0+2N, thus giving a new quantity of 

The copper thus reduced is again oxidized by the oxygen of 
the air setting the nitrogen free; these two reactions really take 
place simultaneously. The gases obtained contained greater or 
lesser quantities of ammonia and aqueous vapor, which may be 
easily gotten rid of by suitable means. 

The chief objection to these processes is the use of copper, which 
is an expensive metal, even in Lupton's process, where it is recovered, 
for it finally undergoes physical modifications, becoming brittle 
and falling to pieces, which prevents its being suitable for further 

The process of obtaining nitrogen by the combustion of char- 
coal in a current of air has the objection of yielding an impure gas, 
always contaminated with carbonic oxide, and even with a small 
amount of oxygen. 

In these various processes the oxygen is lost, as may be easily 
shown. It would therefore be of advantage to extract these two 
gases simultaneously from the atmosphere, i.e. to utilize the residue 
from the preparation of oxygen, a residue which consists entirely 
of nitrogen. 

The same remark may be made concerning the utilization of 
the residual gases of the new industry the manufacture of per- 
oxide of sodium. This product is obtained by passing a current of 
dry and pure air over heated sodium, the gaseous residue con- 
sisting chiefly of nitrogen. 

Any of the methods for the production of oxygen from air may 
be utilized, among which may be mentioned those of Boussingault, 
Tessie du Mothay and Marechal, Mallet, etc. 

Boussingault's process consists in fixing the oxygen by means 
of baryta, there being formed barium dioxide, which under the action 


of A heat and reduced pressure yields one molecule of oxygen, with 
the re-formation of baryta. If care be taken to add certain sub- 
stances so as to prevent fritting, the baryta may be used almost 
indefinitely. This process has the advantage of being rapid, since 
each operation for the complete oxidation and deoxidation lasts 
10 minutes, and 140 may be made per day. 

The process of Tessie du Mothay and Marechal utilizes a mix- 
ture of manganese dioxide and caustic soda. When this mixture 
is subjected to a red heat in a current of air, there is formed sodium 

Mn0 2 + 2NaOH + = MnO 4 Na 2 + H 2 0, 

which, when heated with superheated steam at 450, liberates oxy- 
gen and yields anew the original substances, 

Mn0 4 Na 2 + H 2 = Mn0 2 4- 2N20H + 0. 

The process which was brought out in 1897 by Etard is quite 
similar to the above, in that it also utilizes the oxygen salts of man- 
ganese for the absorption of oxygen; but, as Etard himself says, 
his process does not consist of a simple chemical cycle: it is based 
upon a state of equilibrium. 

If potassium permanganate be subjected to the action of a boil- 
ing alkali, there is produced, under the definite conditions of pressure 
and temperature, a liberation of oxygen, 

2Mn0 4 K + 2KOH = 2Mn0 4 K 2 + H 2 + 0. 

The reaction is, moreover, a reversible one, and if the condi- 
tions of temperature and pressure are changed, the manganate 
.absorbs oxygen of the air and yields again the permanganate. The 
nitrogen set free may be collected by means of suitable apparatus. 
On account of the separation of the oxygen and the nitrogen, this 
process should be tried on an industrial scale. 

As early as 1892, Parkinson installed a similar process in Man- 
chester, which produced 42 cubic meters of oxygen in 24 hours. He 
uses a mixture of kaolin and permanganate, which is heated in 
retorts at a reduced pressure, and even in vacuum. Under these 
conditions the permanganate yields its oxygen. It reabsorbs 
oxygen when heated to 550 C. under pressure in a current of com- 
pressed and hot air. There are five retorts, one of which is used 


for reheating the air. This air is compressed by means of a pump 
in a compressor, whence it is driven to the retorts arranged in such 
a manner that one of them absorbs the oxygen while the other liber- 
ates it. The nitrogen is continually removed by means of a sniffling- 
valve, and the separation of the two gases is automatically regu- 
lated by means of a system of valves. The permanganate mixture 
is very stable, since it is altered neither by moist air nor by car- 
bonic acid. 

Numerous patents have been taken out in regard to the manu- 
facture of oxygen, but they are only more or less successful 
modifications of the processes brought out by Boussingault and 
Tessie du Mothay. 

Mallet's process, which is likewise much to be recommended, con- 
sists in using a 20% solution of cuprous chloride. This solution is 
placed in a retort, which is heated to 100, and a rapid current of 
air is passed through. The cuprous chloride is converted into the 
oxy chloride, which, when heated in the same retort to dull redness, 
loses its oxygen and becomes reconverted into the cuprous chloride. 

Several years ago other rather ingenious processes were shown. 
They are based not upon chemical reactions, but upon purely 
physical phenomena, especially those of dialysis and solubility. 

In the first case the processes are based upon the differences exist- 
ing between the rate of dialysis of nitrogen and oxygen. Of such 
is Villepigne's process, patented in 1896. This consists in causing 
air to pass through a series of membranes made of caoutchouc, 
through which the nitrogen traverses less rapidly than does the 
oxygen, so that at the last membrane the oxygen emerges almost 
pure, leaving the nitrogen behind in each membranous compartment, 
which is removed by special means. 

It is not known that such processes are successful or that they 
are employed on an industrial scale. Nevertheless this is not 
the last to be heard upon this subject, and the future will probably 
show us what to expect from these new methods. 

Finally, another very ingenious process must be mentioned, 
one which likewise is based upon the difference in the physical prop- 
erties of nitrogen and oxygen, and which seems to merit an im- 
portant industrial place. This is the process of Raoul Pictet, who 
is already well known in the scientific world through his remarkable 


researches on the liquefaction of gases. From the " Bulletin de 
la Societe des Ingenieurs civils, " before which, on June 7, 1901, Pectet 
elaborated his new process, the principal features are here extracted 
so as to give a clear idea of this discovery. 

The principle of this method is as follows: The point of lique- 
faction of oxygen under atmospheric pressure is about - 183, whereas 
that of nitrogen under the same conditions is 195. Therefore 
the nitrogen is sensibly more volatile than the oxygen, and the 
difference of 12 which exists between these two boiling-points 
differentiates, as the theory of heat shows, at such low tempera- 
tures, two liquids such as 40 would differentiate at temperatures 
of 60 to 100. 

It is therefore easy to see that if a mixture of these two gases., 
previously liquefied, be vaporized, it will be possible to obtain, 
on the one hand, pure nitrogen, and, on the other hand, equally pure 
oxygen, by a process prefectly analogous to that upon which the 
system of fractional distillation depends. Nevertheless the problem 
is inverted, from a practical point of view, since it is necessary first 
to liquefy the two gases and then to vaporize them in order to collect 
them in the gaseous state. 

Thus, the inventor succeeds in separating the two gases on an 
industrial scale. The air is first suitably dried, then it is compressed 
into an apparatus completely immersed in liquid air. Under the 
influence of the temperature and pressure, this air is in its turn liquefied 
by giving up its latent heat of condensation, under the influence of 
which an equal quantity of the liquid air of the container becomes 
vaporized. In this way, with a very slight expense of energy and 
a definite quantity of liquid air, unlimited quantities of atmospheric 
nitrogen and oxygen may be set free. Now, the difference exist- 
ing between the points of liquefaction of these two gases being 
known, the more volatile nitrogen will escape before the oxygen, 
and it will therefore be possible to collect them separately by means 
of suitable apparatus. In this way three classes of gas are obtained: 

Nitrogen purer than 90.00% 

Oxygen at a purity of 50.55% 

Oxygen purer than 90.00% 

and also carbonic acid, which always exists in air, and which is 
collected in the solid state. 


As will be seen, this is a most ingenious process, practical as well 
as ingenious, and likewise not at all expensive; qualities which seem 
to warrant its coming application on an industrial scale. 

Having firmly established the theory of the formation of cyanides, 
and the remarkable role which is played by atmospheric nitrogen, 
it was immediately attempted to turn this discovery to account. 
At first view, and at least theoretically, nothing seems simpler than 
to combine the three elements, nitrogen, carbon, and alkali metal; 
but the experiments undertaken to fix the nitrogen of he ai:* on a 
practical scale have not always given results which would lead one 
to expect its fulfillment. Nitrogen has in fact quite definite nega- 
tive properties, and its fixation is a difficult problem which has not 
yet been solved satisfactorily, although remarkable progress has 
been made. 

The first attempts to fix nitrogen of the air with a view to the 
production of cyanides have all completely failed. Not one of them 
obtained the support of the manufacturer; nevertheless it is ex- 
tremely interesting to study them, for they are a step toward the 
truth, and they have had an incalculable bearing on the progress 
of this industry. 

Bunsen's Process. This first process was attempted on an 
industrial scale in 1845. This was shortly after the efflorescences 
of potassium cyanide were discovered in the blast-furnaces. Starting 
from the idea that the potassium cyanide formed was due to the 
action of air, Bunsen constructed a special blast-furnace for the 
production of potassium cyanide. Its shape was similar to that of 
ordinary blast-furnaces. It was filled with superposed layers of 
charcoal and potassa and heated to a high temperature by the 
combu tion of a portion of the charcoal. At the same time a power- 
ful current of air was blown through the mass by means of an air- 
exhauster. Under these conditions cyanide of potassium was formed, 
which flowed through the lower part into a receiver ad hoc. The 
product thus obtained was highly contaminated with such im- 
purities as charcoal, alkaline salts, and mineral salts, due to the ash 
of the combustible material, and it could be used only in the prepara- 
tion of yellow prussiate of potash. Besides this serious objection, there 
were others no less serious, such as the losses through volatilization 
and the difficulty of conducting such an operation, especially of regu- 


lating the temperature and the draft of air, all of which caused the 
abandonment of this process. 

Possoz and Boissiere *s Process. This process, successively put 
into operation at Crenelle and at Newcastle, had no better success. 
The principle is the same as in Bunsen's process, differing from it 
only in the modification of the apparatus, which allowed the tem- 
perature and the intake of air to be regulated. Notwithstanding 
their patient efforts and an unceasing struggle of several years, 
these two French chemists were compelled to abandon their project, 
not being able to meet foreign competition, which sold cyanide at 
a lower price than theirs. Yet during the first year of their work 
at Grenelle, in 1843, Possoz and Boissiere succeeded in producing 
15 tons of an excellent quality of ferrocyanide. But the high cost 
of fuel and of refractory brick -at Paris compelled them to go to Eng- 
land. After completing arrangements with Bramwell and Hughes, 
they settled at Newcastle-on-Tyne, where, in 1844, their process 
was established. The process was as follows: 

Small pieces of wood charcoal of good quality were saturated 
with 20 or 30% of caustic potash, or of carbonate of potash moistened 
with a quantity of water just sufficient to dissolve it. After desic- 
cation, this material was charged into vertical retorts heated on 
the outside in a furnace at white heat. 

The retorts were 3.50 meters long, 0.60 m. outside diameter 
and 0.492 m. inside diameter. The upper portion was of re- 
fractory clay and was 0.23 m. in thickness; the lower part, which 
served as cooling-chamber for the cyanide formed, was of iron. The 
height, heated to white heat, was 246 millimeters. A portion of the 
gases of combustion, quite rich in nitrogen, was heated to a white 
heat by passing it through a superheater, where it was compressed 
by means of a pump. On coming out of the superheater, the gases 
penetrated into the retorts through small lateral slits. After 10 hours' 
heating and action of the gases, the cyanide mixture was removed 
automatically and in regulated quantity from the bottom of the 
retort. This mixture was allowed to fall into a cooling-chamber 
and thence into vats containing water and sulphate of iron. By 
means of a similar automatic system a new charge of charcoal and 
potassa was added and the operation repeated. 

Every half hour the apparatus was charged with an amount 


equal to 15 kg. wood charcoal containing 25% potash, and a corre- 
sponding quantity of cyanided charcoal was removed. The opera- 
tion was in this way continuous. 

In 24 hours each apparatus was charged with 720 kg. dry char- 
coal-potash containing 460 kg. wood charcoal and 260 kg. car- 
bonate of potash. During the operation the mass decreased 
one half in volume. It contained from 30 to 50% potassium cya- 
nide. The number of these apparatus was twenty-four, twenty of 
which were in operation, two ready to be used, and two being 
repaired. Each one of them produced 50-70 kg. of ferrocyanide 
per day. 

The net cost at the works in Newcastle, in 1846, was 1.86 francs 
per kilogram, itemized as follows on the basis of 1000 kg. of ferro- 
cyanide of potassium: 

7000 kg. wood charcoal, crushed, @2.50 fcs. per 100 kg 175 fcs. 

1000 kg. potash from America @ 50 fcs. per 100 kg 500 

30 tons coke @ 8 fcs 240 

20 tons coal @ 2.50 fcs 50 

1 ton carbonate of iron, powdered 25 

120 men and children (labor) 375 

Maintenance, wear, interest, etc 500 

1865 fcs. 

Possoz and Boissiere's process was in operation at Newcastle 
during the three years 1844 to 1847. The works produced 1 ton 
of potassium ferrocyanide regularly per day. 

That is certainly an appreciable result, but when the process 
was abandoned, the company could show for this result only a very 
large deficit, due chiefly to the rapid wear and tear of the apparatus, 
which it was necessary to repair frequently, and to the losses in 
carbonates, which amounted to three parts for every one part of 
prussiate produced. Moreover, the amount of cyanided charcoal 
to be subjected to lixiviation was far too small in proportion to 
the amount of ferrocyanide obtained. 

Other attempts preceded or followed that of Possoz rnd Bois- 
siere. But, like this one, they also proved fruitless, and not one of 
them has, to our knowledge, succeeded in giving profitable results. 


The yield was too small to produce a cyanide capable of competing 
successfully. To understand the causes which made these processes 
abortive, one needs only to consider that in such innovations only 
4% of the nitrogen was fixed, that the high temperatures necessary 
in these processes resulted in rapid wear and tear of the apparatus 
and in enormous losses through volatilization, and that moreover 
the product obtained was so impure that it was necessary to purify it 
.at great cost. Yet they deserve to be mentioned. 

Newton's Process. First comes Newton's process patented in 

1843 in England. In this process the inventor causes the gas com- 
ing out of lead chambers to pass over a mixture of charcoal and 
potash, or of charcoal impregnated with 20-30% carbonate of pot- 
ash heated to a suitable temperature. The yield was said to be 
50% of the theoretical. The process was carried on from 1840- 
1847, when it was abandoned, the losses in carbonate of potash being 
enormous and the apparatus deteriorating rapidly. Newton noticed 
that wood charcoal gave better results than coke, that potash was 
preferable to soda, that the yield increased with increase of tem- 
perature, and that water-vapor exerted a detrimental action. In 

1844 Sinndel passed nitrogen over charcoal in closed vessels at a 
high temperature. 

Blairs' Process. Blairs caused nitrogen to be passed over a 
mixture of carbon and potassa in a shaft-like furnace, which was 
heated by a grate placed in the exterior casing. The products of 
cyanide and potash were collected in chambers or in ferric solutions. 
The residual charcoal was treated with water and furnished a fresh 
amount of cyanide. 

Armengaud's Process. This process (1847) differs from the pre- 
ceding in that the inventor operated in the presence of water. All 
these processes, as well as those of Alder (1879) and Weldon (1881), 
-differ from each other only through modifications pertaining to the 
apparatus, with the object of the introduction of air and the produc- 
tion of heat. 

Margueritte and SourdevaPs Process. This process (1862) is 

I the only one which merits more attention. The inventors sub- 

1 stituted baryta for potassa for many well-grounded reasons. 

1 In fact, baryta is much cheaper than potassa, and is in- 

fusible at very high temperatures; moreover, as is well known, 


barium fixes nitrogen with great ease. (It would even be ideal to 
find masses of barium or calcium in order to fix the nitrogen of the 
air. Lithium has also been mentioned, but it is a rare element 
and too difficult to prepare.) It attacks the apparatus much less 
than does potash, and the wear and tear of the vessels is diminished 
because the temperature necessary for the formation of barium 
cyanide is much lower than that of potassium cyanide. 

This process may be operated in different ways. First a mixture 
is made consisting of carbonate of barium with 20 to 30 parts of 
tar, resin, pitch, wood charcoal or coke, which mixture is heated 
to high temperature under the action of a current of air. Under 
these conditions the baryta absorbs nitrogen with ease, with forma- 
tion of barium cyanide, which is converted into alkali cyanide by 
double decomposition by the reproduction of barium carbonate : 

2C+2N + Ba = (CN) 2 Ba, 
(CN) 2 Ba + CO 3 K 2 = 2NCK + C0 3 Ba. 

This is one of the rare processes invented along this line which 
has given good results, and inventors have appeared to be well 
satisfied with its industrial practicability. 

Mond's Process. Margueritte and Squrdeval's process was taken 
up in America in 1882 by Mond, who modified it somewhat, and 
who obtained from it good results. Mond used a mixture consist- 
ing of charcoal, magnesia, and carbonate or oxide of barium pre- 
viously ignited out of contact with air. 

According to his German patent No. 21175 (1884), he operated 
as follows: 

Briquettes composed of a mixture of witherite (natural carbonate 
of barium), pulverized wood charcoal or coke, and pitch in the fol- 
lowing proportions: 

Carbonate of barium .............. 32 parts 

Wood charcoal .................... 8 " 

Tar .............................. 11 " 

These briquettes were submitted to the action of a reducing 
flame in such a manner as to char the pitch and to dissociate the 
carbonate of barium. 


They were then ranged in an annular furnace, where there was 
directed a current of gas rich in nitrogen and as poor as possible 
in oxygen, carbonic acid and water-vapor; for example, that which 
escapes from the carbonic-acid absorption apparatus in the ammonia 
soda process. This gas was previously heated to a temperature 
about 1400. In order to do that, it passed through into the first 
furnace containing briquettes already cyanated, which it cooled 
while at the same time heating itself. On coming out of this fur- 
nace, it passed into a Siemens regenerator, and from there into the 
furnace where the reaction takes place. When the mass was thought 
to be sufficiently cyanated, it was drawn out of the furnace, care 
having first been taken to have the contents of the furnace cooled 
to about 300. The yield was about 40%. 

Weldon's Process.^Weldon (1879) made use of a revolving 
furnace similar to that employed in the manufacture of soda and 
in which at a dull-red heat he caused nitrogen to act upon a mix- 
ture of charcoal and alkali. 

Fogarty's Process. To the above must be added the processes 
patented in America in 1883 and 1887 by Fogarty and Dickson 

Fogarty begins by producing a heating gas highly superheated,, 
and consisting of a mixture of carbon monoxide, hydrogen, and 
nitrogen. Then he causes this gas to pass into retorts, into which 
he transmitsi n the same direction a measured volume of hydro- 
carbon vapors obtained from the distillation of oils. The mixture 
of gases comes in contact with a definite quantity of powdered 
incandescent lime, which falls from the top of the retort. This 
gas contains, therefore, no oxygen nor carbonic acid and the hydro- 
carbons are consequently broken up into acetylene, carbon, and 
hydrogen, which, in contact with lime and nitrogen, produce cal- 
cium cyanide. 

The reaction may take place in two ways: 

(1) Either by the combination of nitrogen and calcium with 
acetylene at the temperature at which this gas is formed, (2) or 
by the union of nascent carbon produced by the decomposition of 
acetylene, C2H2 = C2 + H 2 , with nitrogen and calcium. 

The experiments, of Fogarty justify this hypothesis, the most 
favorable temperature for the reaction being 2200 to 2300 F. 


Dickson's Processes. Dickson injected a mixture of air, water- 
vapor, and powdered charcoal into a chamber filled with 
powdered alkali and heated to a proper temperature, naturally 
quite high. This heat was produced by the combustion of the 

Lambilly's Process. Not till 1889, with the appearance of the 
processes of Lambilly and of Chabrier, have real improvements 
in the manufacture of cyanides been noted. These two inventors 
sought first of all to produce ammonia from the nitrogen of the 
air by passing through cyanides. Their various patents show a 
deep knowledge of the phenomena of cyanuration. 

The first two of these patents were taken out with a view espe- 
cially toward the production of ammonia through the interme- 
diary of the cyanides. The first one (No. 199977), taken out 
August 8, 1889, is based on the following well-known facts: 

(1) The volatile hydrocarbons are decomposed at a red heat 
into hydrogen and more condensed carbides. 

(2) When nitrogen comes in contact with nascent hydrogen, it 
unites with it to form ammonia if the temperature is lower than 
that of the decomposition of this latter body. 

(3) The oxides of the alkalis or alkaline earths are reduced in 
the presence of charcoal and absorb nitrogen in order to form cya- 
nides at temperatures naturally varying with the kind of oxidizing 
agent used. 

The inventors proposed to operate this process on an industrial 
scale as follows: 

The hydrocarbon gas is produced by the distillation of coal, 
wood, peat, petroleum; the nitrogen is obtained from the atmosphere 
from which it is extracted by processes already known (those of 
Tessier du Motay, Boussingault, or Mallet). It is mixed with the 
carbide gas in amounts varying with the composition of the hydro- 
carbon. This gaseous mixture passes through a series of cylindrical 
retorts arranged in one or more furnaces. These retorts are charged 
with a mixture of charcoal and oxide of alkali or alkaline earth 
and the whole heated to redness. The inlet of gas is stopped when 
the amount already taken in is judged to be sufficient to convert 
the contents of the retorts into cyanide. Under these conditions 
the hydrocarbon gas is broken up. Its decomposition goes on 


and is completed at the temperature at which it begins, if care be 
taken to remove the gases formed from the atmosphere in contact 
with the substance undergoing dissociation, in such a manner that 
the pressure is always less than the tension of dissociation. This 
condition is found fulfilled; in fact, the formation of ammonia by 
the union of nascent hydrogen and nitrogen takes place with con- 
traction. There is thus produced a partial vacuum which, together 
with the carrying away of the ammonia, causes a pressure inferior 
to the tension of dissociation. The carbon of the carbide, being 
in the nascent state in the presence of nitrogen and of substances 
capable of becoming converted into cyanides, yields this latter 
body. According to the inventors, if the conditions of temperature 
and pressure are fulfilled, it is possible to fix an amount of nitrogen 
corresponding theoretically to the hydrogen and to the carbon 
of the carbides used. 

An ingenious modification of the above process is that brought 
out by Lambilly and Chabrier in the second patent (No. 202700) , 
of December 21, 1889. It consists in removing the hydrogen from 
the mixture of hydrocarbons and nitrogen before its entrance into 
the cylinder where the conversion into cyanide is to take place, 
and for the following reasons: 

Illuminating-gas is composed of methane and ethylene, which 
are broken up at red heat into hydrogen and acetylene. In the 
presence of nitrogen and of bodies which may be converted into 
cyanides, acetylene gives rise to these latter, but the hydrogen set 
free with acetylene through the decomposition of the hydrocarbon 
places, because of its tendency to recombine with the acetylene, 
a serious obstacle in the way of the formation of cyanogen, which 
therefore takes place but slowly. It is therefore necessary to rapidly 
remove this hydrogen, by combining it with nitrogen under the 
form of ammonia, before the appearance of the mixture of acety- 
lene and nitrogen into the cylinder where the cyaniding is to take 
place. For this purpose the gas first passes through a cylinder 
containing oxide of copper, obtained from the process of extracting 
atmospheric nitrogen by the use of this metal. It reduces the oxide 
of copper and thus forms anew the metal, which may be used in 
the preparation of fresh quantities of nitrogen. The hydrogen being 
eliminated by this means, the gaseous mixture, which consists now 


of only acetylene and nitrogen, passes into the second cylinder 
containing the substances to be converted into cyanide. The flow- 
ing and the outlay of gas and of nitrogen are regulated through 
the result of the combinations. The inventors claim that in this 
way a minimum of 1 cubic meter of nitrogen may be fixed; that 
is, 1.25 kg. per cubic meter of illuminating-gas used. 

In his patent No. 210365 of December 20, 1890, Lambilly seeks 
only the production of cyanides. This patent is extremely inter- 
esting, its chief object being to produce nascent carbon, which renders 
its union with nitrogen all the easier. 

It still depends on the decomposition of illuminating-gas in an 
atmosphere of nitrogen and in the presence of substances capable 
of being converted into cyanides. But the decomposition of the 
gas is carried on under certain conditions which permits a gas 
extremely rich in acetylene (C 2 H 2 ) to be obtained, which is finally 
resolved into its elements. In order to carry on this dissociation, 
the inventor starts from the consideration that illuminating-gas 
is a mixture varying more or less, according to its method of 
preparation, in the amounts of hydrogen (a gas containing the 
least possible amount of this element should be prepared), and 
the three hydrocarbons, ethylene, methane, and acetylene, and that 
these three bodies are decomposable at different temperatures. 
In fact, acetylene is broken up into its elements only in the neigh- 
borhood of a white heat, while at a red heat ethylene breaks up 
into acetylene and hydrogen, or methane and hydrogen, or a mix- 
ture of these three gases according to the degree of redness and 
the time to which it is subjected to this temperature. Methan 
is decomposed at a like low temperature into acetylene and hydro- 
gen. From these facts the inventor concluded that if care be 
taken at the beginning to limit the action of the temperature, 
only the ethylene and methane will be decomposed, forming a 
mixture very rich in acetylene, which will combine with the acetylene 
already existing normally in the gas. Then by raising the tem- 
perature to a white heat, the acetylene will in its turn be dissoci- 
ated into its elements. 

The manufacture of cyanides by this method will therefore 
comprise four phases: 

(1) The preparation of nitrogen. 


(2) The preparation of illuminating-gas. 

(3) The dehydrogenation, or, better, the carbureting of the 

(4) The conversion into cyanides. 

The nitrogen is prepared as in the previous method, by passing 
air over copper heated to dull redness. The gas is prepared by 
the usual methods, then freed from its hydrogen by passing it 
over copper oxid produced in the preparation of nitrogen. The 
mixture which is to be converted into cyanide is composed of char- 
coal and oxids or carbonates of the alkalis or of barium finely 
powdered. This is placed in cylindrical retorts and heated to a 
.high temperature, which should not, however, reach a white heat. 

Right here Lambilly improved the methods of his predecessors in 
two important particulars viz., in the use of the materials for manu- 
facturing cyanides. Having noticed that when the alkali and charcoal 
.are heated there is formed a considerable amount of carbon monoxid, 
which prevents the intimate contact of the substances which are 
to be converted into cyanide with the current of nitrogenized and 
carbonized gas, he avoids the passing of this gas just as soon as 
the temperature is favorable for the formation of cyanides, and 
removes the carbon monoxid as fast as it is formed. For this pur- 
pose he makes use of the principle established by Sainte-Claire 
Deville 1 , that the dissociation of a body continues and ends at the 
temperature at which it begins provided care be taken to remove 
the products of dissociation. In this way Lambilly economizes 
fuel, for the dissociation of the alkali oxid takes place at a rela- 
tively moderate temperature, and, moreover, he uses the carbon 
monoxid in heating the furnaces in which the cyaniding process 
proceeds. From the moment carbon monoxid ceases to be formed, 
he allows the mixture of gas and nitrogen to pass. 

The second improvement quite naturally follows from the 

In fact, being no longer troubled by carbon monoxid, the mix- 
ture of gas and nitrogen may be allowed to come under pressure 
into the cylinder where the cyaniding process goes on, by giving 
to the hydrogen, which is the residue of the reaction, but a limited 
outlet. In this way a more intimate contact of the substances 
to be converted into cyanides with the reacting gases is obtained, 


In order to hasten the decomposition of the carbides and the 
foimation of the cyanides, Lambilly proposes, moreover, to add 
to the mixture of charcoal and alkali a certain proportion of small 
pieces of nickel, iron, or cobalt, which exert a decomposing action 
on the carbides, and which, becoming heated more easily than does 
the mixture which is to be converted into cyanide, yields to this 
mixture a part of its heat. 

The examination of these methods shows that the inventor 
strove always to produce more and more, in a state as near as pos- 
sible to the nascent state, substances which are to react upon one 
another. This is the object of the later patent dated December 
31, 1900, and which allows the carbon monoxid produced in the 
reduction of the alkali oxids to be profitably utilized. 

Lambilly proposes to collect this carbon monoxid in a gasometer, 
then to mix it with a quantity of illuminating-gas such that the 
hydrogen resulting from the decomposition of the latter may com- 
bine with the whole of the oxygen of the carbon monoxid, the acety- 
lene thus formed yielding a fresh amount of carbon in the nascent 
state. This ingenious arrangement economizes more than half 
the illuminating-gas. 

In his German patent No. 6377 (November 14, 1890, March 14, 
1892), the only new fact given by Lambilly is the manner in which 
he obtains the alkaline mixture which is to be converted into cyanide. 
In order to make caustic the alkali or alkaline earth which is to 
be used in producing cyanide, carbonate of potash or of barium 
is used, and in order to render them porous and permeable to the 
action of the reacting gases, there is added for each equivalent of 
carbonate used (69 kg. K 2 C0 3 or 98 kg. BaC0 3 ) 20 kg. of charcoal 
and a like amount of quicklime. The whole is worked up into 
a dry powder, introduced into horizontal cylinders connected with a 
vacuum pump, and heated under as perfect a vacuum as possible. 
Under these conditions the carbonate becomes caustic, and the 
carbonic acid produced by the reaction is reduced on contact with 
the charcoal into carbon monoxid, which is utilized as fuel. The 
inventor also states the amount of pressure under which he trans- 
mits the mixture of illuminating-gas and nitrogen into the cyaniding 
cylinders. This pressure should equal 10-15 centimeters of mer- 


The processes of Lambilly are still far from being perfect; yet 
they are extremely interesting to remember. At the time of their 
appearance they produced certain practical results which were 
by no means to be despised. Besides they show a considerable 
progress over the first synthetic processes used, a progress obtained 
through a profound study of the complex reactions which take 
place in the formation of cyanides, and which are the result of wise 
observations and of the patient efforts of their inventor. One 
could almost affirm that they paved the way for the really synthetic 

The following processes produce cyanides by the action of nitro- 
gen on a mixture of caustic alkali or carbonate of alkali and char- 
coal. They differ but little from one another. 

Gilmour's Process. First comes this process (French patent 
No. 233175, October 2, 1893; German patent No. 8475, September 2 y 
1893). It consists in producing cyanide compounds by the action 
of atmospheric nitrogen on a mixture of alkali and charcoal heated 
to 1000. 

The various caustic alkalis or their carbonates may be used 
at will; however, the inventor prefers the use of caustic potash. 
These substances are mixed in about equal proportions with char- 
coal, the mixture is placed in suitable recipients through which 
nitrogen extracted from air is made to pass until the mass is more 
or less transformed into cyanide. The vessels are then emptied 
and the resulting product treated with water. The hydrocyanic 
acid of the cyanides in solution is displaced by means of a current 
of carbonic acid (this is preferably done at boiling temperature 
and under atmospheric pressure), and absorbed in a concentrated 
solution of caustic soda, where it forms sodium cyanide, which is 
separated. The carbonic acid is produced by the combustion of 
charcoal in air, an operation which allows the production of nitrogen 
necessary for the first reaction. Moreover, this carbonic acid pro- 
duces anew the alkali used for the cyaniding process. 

Young's Process. This process (English patent No. 24856, Dec. 
27, 1893) is but slightly different. The cyanide is obtained by pass- 
ing a mixture of air and hydrocarbon vapors over the following 
mixture heated at a high temperature in iron or earthen retorts or 
in suitable furnaces: 


Caustic or carbonate of alkali 4 parts 

Hydrate or carbonate of alkaline earth 1 part 

Coke or coal 2 parts 

The resulting product is treated with water in order to extract 
the cyanide. When the temperature is too high a portion of the 
cyanide distils. This portion may be collected by causing the gases 
with which it is carried away to pass through a layer of vegetable 

William Donnell Mackey's Process. This process (French patent 
No. 243136, Nov. 25, 1894; German patent No. 87366, Nov. 28, 1894) 
is quite similar to that of Bunsen. It consists simply in subjecting 
to a powerful current of air a mixture of coal, wood charcoal, or 
coke, lime, potash, or any other alkaline compound which may be 
reduced by the charcoal. This mixture is charged in a specially 
constructed furnace A (Fig. 3) through the hopper E and heated 
to a very high temperature. The furnace is vertical and quite 
large. It is provided with lateral openings to which are joined 
two series of tuyeres. These are arranged in two series, BB and CC, 
one at one eighth the height of the furnace, the other at about the 

The cyanide formed is sucked away by a machine through the 
opening D situated in the space included between the two series 
of tuyeres. 

Thes are worked by a powerful bellows. The cyanide is col- 
lected and condensed according to ordinary methods. 

The gases produced through combustion escape through the 
horizontal pipe F. 

Readmann's Process. Readmann's process (French patent No. 
243129, Nov. 26, 1894, March 12, 1895) differs from Gilmour's process 
just cited only in the fact that the inventor uses the electric arc 
in order to produce the necessary temperature. In this way he 
claims that all waste and destruction of apparatus is avoided because 
he develops the heat in the very mass itself by means of carbon 
electrodes or electrodes of other suitable materials. 

The mixture to be con verted into cyanides is composed as follows: 

Carbonate of barium (perfectly dry) 50 kg. 

Powdered charcoal (wood charcoal or oil or coke). . . 10 " 


The carbonate of barium may be replaced by any other car- 
bonate or oxid of alkali or alkaline earth. 

The intimate mixture of these substances is introduced into 
the crucible which contains coke previously heated to incandescence. 
As source of nitrogen the inventor uses air more or less deoxygenized, 
or water-gas, whose denitrified residue may be used either as fuel 
or for illuminating purposes. The cyanide formed flows out through 

FIG. 3. Mackey's Process. 

a lateral opening situated on the bottom of the crucible. The 
volatilized portion carried off with the remaining gases passes into 
a receiver or condenser, where it is absorbed by well-known 

Mehner's Process. Ch. Mehner of Charlottenburg has patented 
a similar process, which consists in passing a current of hot air, or 


of any other gas rich in nitrogen, over a mixture of coke and car- 
bonate of alkali or alkaline earth heated to a white heat in the 
vat of an electric oven. The volatilized cyanide together with 
the other gases are conducted into a system of condensers filled 
with coke placed above the level of the electrodes. 

Swan and Kendall's Process. In order likewise to avoid the 
wear and tear of the apparatus, Swan and Kendall have devised 
an ingenious though complicated arrangement the net cost of which 
must be quite high (French patent No. 252071, Nov. 24, 1895, and 
March 13, 1896, and German patent No. 87786, Nov. 28, 1895). It 
consists of an inner vessel constructed of thin sheets of nickel or 
cobalt, surrounded by another larger vessel made of refractory 
earth. This apparatus is placed in an oven which is slightly inclined. 
The inner vessel is provided with a platinum extension. Hydrogen 
circulates in the annular space between the nickel vessel and its 
refractory sheath; its object is to prevent the metal from being 
attacked. First a mixture of carbon and tungsten is prepared, 
consisting of 100 parts of the former to 15 parts of the latter, by 
moistening granular or powdered charcoal with a solution of potas- 
sium tungstate, drying, and igniting. This mixture is placed in 
the inner vessel; a current of nitrogen extracted from air is passed 
through and the temperature raised to redness. When this tem- 
perature has been attained, melted carbonate of potash in variable 
amounts is poured into the crucible. The cyanide formed flows 
out through the platinum extension as fast as it is produced. Tung- 
sten may be replaced by titanium, molybdenum, chromium, or 

Pestchow's Process. In his process, Pestchow of Dantzig (Ger- 
man patent No. 94114, Dec. 8, 1896) has not introduced any great 

It consists in causing a current of nitrogen containing or free 
from oxygen, mixed with or free from ammonia, and carrying 
a certain amount of hydrocarbon e.g. acetylene or powdered 
charcoal, to act on an alkali bath kept in a state of fusion. This 
bath is placed in a covered crucible provided with an opening through 
which the nitrogen gas mixed with hydrocarbons passes. The 
nitrogen should always be in excess, but not the carbon. To the 
alkali bath may be added a certain amount of cyanide from a pre- 


vious operation in order to raise the temperature of the fused 

Chipmann's Process. The latest process of this class is that of 
Chipmann, at Johannesburg (French patent Nos. 275570, March 4, 
1898, and 275488, March 9, 1898), which produces at the same time 
cyanide and sulphocyanide by the action of a current of nitrogen 
to which sulphurous acid has been added, on a mixture of charcoal 
and oxid or carbonate of alkali or alkaline earth. 

First a mixture of equal parts of charcoal and oxid or carbo- 
nate is made. Preferably, carbonate of barium is used. 

This mixture is heated to about 1000 in suitable vessels; then 
a current of sulphurous acid free from oxygen is passed until the 
whole mass has been converted into cyanide and sulphocyanide. 
IVhen this result has been attained, the vessel is emptied and the 
product treated with water. Into the solution thus obtained, heated 
to boiling and after the addition of an oxidizing agent, when 
necessary a current of air is made to bubble under atmospheric 

The carbonic acid of the air precipitates the barium as carbo- 
nate, which is collected, dried, and used over again. The hydro- 
cyanic acid set free passes into condensers containing a concen- 
trated solution of caustic soda kept at a temperature of 40 F. The 
sulphurous acid produced by the decomposition of the sulphocyanide 
is collected with the. nitrogen and used in the next operation. 

Most of these processes have had but a short life industrially. 
That is because the circumstances which affect the yield are numer- 
ous, and a simple thing may change and at the same time modify 
the nature of the reactions. They are therefore but very imper- 
fect methods, to which many and serious disadvantages are inherent. 

The temperature necessary to carry on the reaction is in all 
cases very high: in some cases a white heat, in other cases a cherry- 
red heat. In all cases the heat must be sufficient to cause the reduc- 
tion of the alkali compound used, and there are few apparatus which 
are capable of resisting such a high temperature without wear and 
deterioration. Another disadvantage of this high temperature 
is in the loss due to volatilization either of alkali or of cyanide, 
loses which sometimes amount to considerable. The substances 
used must also be as anhydrous as possible, water converting the 


cyanide into ammonia. Nevertheless, Langlois, Kuhlmann, Armen- 
gaud, and Ertel have shown that the presence of a very small 
quantity of water helps along the reaction, for according to Kuhl- 
mann the production of cyanogen is preceded by the formation of 

The mixture of substances to be converted into cyanide must 
be as perfect as possible, and all means must be taken to make it 
porous and permeable to the action of the reacting gases. The yield 
decreases in proportion as the cyanide is formed, for the fragments 
of the mass to be converted into cyanide, and especially the char- 
coal, becoming imbedded in the cyanide and melted alkali, come 
less in contact with the gases. If the contact surface of these sub- 
stances is too small, the same trouble is met; the apparatus 
should be quite large in order to present as much surface as pos- 
sible to the action of the nitrogenized gas. If care be not taken 
to remove the products as fast as they are formed, that also will 
impede the reaction, which will either be stopped or rendered slower. 

If the substances under treatment contain foreign substances 
without effect on the reaction, these will absorb a portion of the 
heat, whence comes a loss of calories. Moreover, these bodies pre- 
vent the intimate contact of the products of the reaction. 

Likewise, if the gases enclose foreign elements such as oxygen, 
hydrogen, carbon monoxid, or carbonic acid, they all have the 
disadvantage of diluting the nitrogen, which causes the reactions 
to go on more slowly. Moreover, each one of them exerts a detri- 
mental action upon the reactions. Thus it is that carbonic acid 
oxidizes the charcoal, and possibly also the cyanogen. As has 
often been demonstrated, oxygen and cyanogen cannot coexist 
at high temperatures. As to carbon monoxid, some investigators 
attribute to it an injurious action in that it prevents intimate con- 
tact of the cyaniding masses with the nitrogen, whereas others look 
upon it as favorable to the reactions because of its reducing prop- 

The formation of cyanides in these various processes has been 
the subject of much controversy. 

Relying upon many experiments, and especially upon the fact 
that a mixture of acetylene and nitrogen, under the influence of 
the electric spark, yields hydrocyanic acid, Berthelot supposes 


that when charcoal and potassa are strongly heated they give rise 
to a compound C2K 2 , which, fixing nitrogen, then yields potassium 
cyanide, CNK. 

Most of the investigators agree in saying that the union of car- 
bon and nitrogen can take place only at the temperature at which 
the alkali metal is set free. This hypothesis is confirmed by the 
very fact that cyanogen and oxygen cannot coexist in the same 
medium at a high temperature. 

As to the alkali metal, some investigators attribute to it a simple 
contact action, and its object would therefore be to fix the cyanogen 
just as fast as it is formed, in accordance with the law of Sainte- 
Claire Deville, according to which reactions are continued and 
finished quickly if care be taken always to remove the products 
formed as fast as they appear. 

Finally, other investigators assert that there is first a formation 
of an alkali nitride, which later becomes converted into cyanide 
through the action of carbon. This last hypothesis is just as prob- 
able as the preceding ones, since Center and Brieylieb obtained 
cyanide by heating magnesium nitride in a current of carbonic acid 
or carbon monoxid. 

Several processes have even been proposed along this line, e.g. 
those of Moise (French patent 246587, April 22, 1895) and of Mehner 
(French patent 254273, Feb. 26, 1896). 

Processes of Moise and Mehner. Moi'se's process consists in 
heating, in a rotatory oven to a dull red, a mixture of boron 
nitride, alkali carbonate, and charcoal in the following proportions: 

Boron nitride ............................. 50 kg. 

Carbonate of alkali (potassium) ............. 250 ' ' 

Charcoal .................................. 30 " 

The reaction is as follows: 

Boron nitride is obtained by heating to a bright red for one 
hour the following finely powdered mixture: 

Sodium borate ............................. 100 kg. 

Sal ammoniac.., , 150 " 


This product is treated with boiling water, then hydrochloric 
acid is added in excess, yielding a precipitate of boron nitride. 

Mehner prepares nitrides of boron, silicium, magnesium, titanium, 
and vanadium by reducing the oxids of these metals by means of 
carbon in the midst of an atmosphere of nitrogen. 

There is very little probability that these processes have given 
any practical results, and we doubt very much whether they have 
ever been operated industrially. 

Besides, the metals which these investigators used in the prepa- 
ration of the nitrides are too expensive to allow these processes 
to be used practically on an industrial scale. 

All these processes just described have the disadvantage that 
they do not produce the cyanide directly; hi fact, masses contami- 
nated with impurities are obtained which must be treated with 
water and purified, by which the net cost is increased. It has 
already been seen that other equally serious disadvantages are 
inherent to these processes. 

It has already been stated that the cyanide is formed only in 
case the alkali metal is set free. It was therefore quite natural 
that attempts should be made to use this metal in the free state 
in order to avoid the reduction of its compounds originally used 
and* consequently the many disadvantages resulting therefrom. 
These processes may really be designated as synthetic, since they 
start with three bodies in the free state: carbon, nitrogen, potas- 
sium or sodium. The low cost of the alkali metals and the ease 
with which they are at pres nt manufactured permit their use on 
an industrial scale. Moreover, the cyanide industry creates, by 
means of these processes, a new market for the sodium; its use 
became limited when it was no longer employed in the manufacture 
of aluminum. The experiments carried on along this line have 
been satisfactory. They are exceedingly interesting and they will 
therefore be described. 

Castner's Process. This, the first one of these processes, was 
patented by Hamilton Young Castner (No. 239643, June 28, 1894). 
It consists in the action of a current of nitrogen on charcoal heated 
to redness, upon which melted sodium or potassium flows, the reac- 
tion being as follows: 

K or Na+C+N = CNK or CNNa. 


The reaction is carried on in a vertical iron retort (A, Fig. 4) 
placed in a furnace and capable of being heated to redness. This 
retort is provided with an inlet tube B, an S-shaped opening at 
the bottom (7, and with a hopper D. 

FIG. 4. Castner's Apparatus. 

The retort is charged with wood charcoal through the hopper D, 
which is afterward closed. The opening at the bottom C is sealed 
at the elbow E by means of cyanide. The temperature is raised 
to redness, then a current of nitrogen, through the tube F, and 
melted sodium or potassium, through the inlet tube B, are let in 
simultaneously. The alkali metal flows gradually through the 
wood charcoal and meets the nitrogen, which flows in the opposite 
direction. The three elements combine directly and form cyanide, 
which flows through the opening C into the receiver G. The unab- 
sorbed gas escapes through the tube 77, whence it may with advantage 
be conducted into a second retort. Charcoal may be replaced by 


inert substances such as pieces of iron or of porcelain, in which case 
a mixture of nitrogen and hydrocarbon is conducted through the 
mass. The alkali metals may also be replaced by their alloys ; e.g. 
lead sodium. 

Castner has improved this process, which consists in using 
ammonia, and conducting the operation in two stages. This modi- 
fied process will be taken up at length when discussing the ammonia 
processes. Castner's process, properly speaking, belongs to that 
class of methods using atmospheric nitrogen, the only one to which the 
term synthetic really belongs, but to our knowledge it has never 
given results permitting its use industrially. 

Hornig and Schneider's Process. This process belongs to the 
same class as that of Castner. Castner's process consists in allow- 
ing nitrogen to act upon the vapors of the alkali metals in the pres- 
ence of incandescent charcoal; Hornig and Schneider's process 
uses' the alloys of the alkali metals and of the heavy metals. Both 
of these processes using nitrogen or ammonia indifferently, but 
preferably the latter, will be studied in detail in the chapter devoted 
to the ammonia processes. 

Mehner's Process. Mehner's process (1894-1895) belongs in 
some respects to that class of processes using atmospheric nitrogen 

It consists in electrolyzing barium cyanide in a state of igneous 
fusion, using a charcoal cathode and in the presence of nitrogen gas 
(Fig. 5). 

The current decomposes the barium cyanide into hydrocyanic 
acid, which escapes at the anode, and barium, which is set free at 
the cathode at a rather high temperature, close to its boiling-point. 
Meeting the nitrogen, which is in contact with red-hot charcoal 
at the cathode, this metal reproduces cyanide of barium, which 
flows in the bath and is thus subjected to electrolysis. In this way 
the process may be continued. With the same quantity of cyanide 
somewhat limited, it suffices to supply carbon and nitrogen and 
to maintain the temperature desired. The hydrocyanic acid gas 
formed may be conducted outside and absorbed by well-known 
means, or may be fixed in the electrolyzer itself by the addition 
of sea salt, which under the action of the current breaks up into 
chlorine and sodium. The hydrocyanic acid set free at the posi- 
tive pole in a separate cell may, by means of a suitable contrivance, 


react upon the alkali metal displaced and yield cyanide of sodium 

The last class of processes utilizing atmospheric nitrogen is 
based on the use of metallic carbides. It has already been stated 
that many investigators, especially Berthelot, explained the for- 
mation of cyanides through the intermediary of carbides. In 
Comptes Rendus, 1894, 503, Moissan reported that when nitrogen 
is passed over heated carbides of calcium, barium, or strontium 
no reaction or union takes place. Frank and Caro showed that 


FIG. 5. Mehner's Apparatus. 

the opposite was true if the nitrogen used was charged with a cer- 
tain amount of aqueous vapor. In this case cyanides are formed 
as follows: 

C 2 M+2N=(CN) 2 M. 

Based upon this reaction, these investigators have brought 
out a process for the manufacture of cyanides which is thought 
to give satisfactory results. Many other manufacturers have fol- 
lowed the example set by Frank and Caro, and have had similar 
processes patented. 

Frank and Caro's Process. The first patent taken out by Frank 
and Caro dates from 1895 (French patent No. 249539, Aug. 10, 1895). 


It consists practically as follows: It may be applied equally well 
to the carbides of the alkaline earths or alkalis, either pure or con- 
taining alkaline earths or alkalis, or even salts of these bases. A 
mixture of the carbides prepared in the usual manner may like- 
wise be used; but according to the opinion of the investigators, 
barium carbide is the most suitable. 

The carbide prepared in the usual way is disintegrated and 
introduced into a tubular retort of refractory material, preferably 
clay. This retort is provided with suitable tubes for the inlet and 
outlet of gases. 

The necessary nitrogen is taken from the atmosphere. Air 
either wholly or partly free from oxygen may be used. The air 
is charged with moisture by passing it through a vessel containing 

The retort is first heated almost to redness, then the current 
of nitrogen, charged with moisture, is admitted under a moderate 
pressure and at such a rate that the reaction is complete in about 
two hours. A change of 15 to 17 kg. barium carbide requires 2 to 
2.5 cu. m. of nitrogen. 

The product obtained is cooled, then taken up with water. The 
unconverted carbide yields acetylene, which is collected separately. 
The solution contains barium cyanide which by double decom- 
position may be transformed into alkali cyanide. 

Carbide of calcium alone, thus treated, does not yield good 
results. An excellent yield is obtained, however, by using a mix- 
ture of calcium and barium carbides or of carbides of calcium and 
sodium obtained by the ordinary methods by means of soda lime 
and charcoal. The product of the reaction is treated as just stated 
i.e. treated with water the acetylene being collected separately 
and the solution thus obtained converted into alkali cyanide. This 
latter operation may be brought about either by addition of an 
acid or preferably by conducting carbonic acid through the solution, 
which displaces the hydrocyanic acid gas, which latter is brought 
in contact with the metallic oxid of the cyanide desired. This 
may likewise be effected by double decomposition by the addition 
to the solution of an alkali ca bonate, which transforms the cyanide 
of the alkaline earth into alkali cyanide, while at the same time 
the carbonate of the alkaline earth separates out. 


The result given by the treatment of the carbides of barium 
or calcium may be improved by adding to the carbides or to their 
mixture an alkali carbonate or hydrate. 

When the alkali carbides, whether alone or mixed or even in 
the presence of an alkaline earth or its salts, are subjected to the 
same treatment as that indicated above in the case of the barium 
carbide, they yield the corresponding cyanides, which may easily 
be extracted with water from the product of the reaction. 

The most favorable temperature for these reactions is, according 
to the investigators, dull redness. If a lower temperature be used 
the action of the nitrogen takes place but slowly, while if the tem- 
perature be too high the yield decreases, due to a partial decom- 

In order to make the most profitable use possible of the nitrogen, 
several retorts may be used in a series, which allows a continuous 
operation . 

In the certificate of improvement joined to the patent just 
described, Frank and Caro replace nitrogen with ammonia. 

The investigators state that in practice the formation of cyanides 
depends not only on the action of free jdtrogen, in the presence of 
water- vapor, on the carbides, but also on the action of dry nitrogen 
upon impure carbides containing oxids, carbonates, and sulphates. 

Moreover, the chemically combined nitrogen (ammonia or 
the oxids of nitrogen) may likewise be used in the formation of 
cyanides by means of carbides if the nitrogen compounds used 
furnish, during their action on the carbides, the necessary nitrogen, 
a result which is brought about through dissociation or reduction 
by means of carbides. From these remarks the investigators think 
that the oxids, carbonates, sulphates, or other salts induce the 
reaction in the same manner as does water-vapor, the use of which 
may thus be suppressed. This action of foreign salts is shown 
even when the carbides contain only very small quantities of them. 

Likewise, with the object in view of avoiding the use of water- 
vapor, the inventors of this process recommend the use of ammonia, 
which renders the action of moisture superfluous. 

If ammonia be passed over a carbide or a mixture of carbides, 
or a mixture of carbides and alkali salts, cyanide is formed. During 
this formation, the ammonia becomes dissociated into its constitu- 


ent elements, nitrogen and hydrogen. The nitrogen becomes fixed 
to the metal, whereas the hydrogen escapes, and may be collected 
separately and used as such in the heating of the apparatus. The 
reaction may be thus interpreted: 

CaC 2 +2NH 3 = Ca(CN) 2 +3H 2 . 

Although the presence of moisture is useless in starting and 
completing this reaction, it does not modify it in any way, and 
exerts no perceptible action on the yield. Thus ammonia-gas, 
whether dry or moist, could be used equally with advantage. 

Continuing their researches on the manufacture of cyanides 
by means of carbides, Frank and Caro observed: 

(1) That the formation of cyanides by the processes above 
mentioned is however limited, and if the heating be carried on at 
least up to a dull redness and does not exceed a bright yellow, a 
large part of the nitrogen absorbed by the carbides is combined 
at the expense of the formation of other nitrogenous compounds. 
This phenomenon is, according to them, due in part to the action 
of cyanides already formed, and in part to the direct action of the 
reacting mass according to the two general equations 

z(2MCN) +zN = z(M 2 NCN) + (CN)s, 
M 2 C 2 +N 2 =M 2 NCN+C. 

In fact Frank and Caro discovered that the reaction masses 
contained appreciable amounts of metallic derivatives of cyanamid, 
(M 2 NCN), of paracyanogen (CN)z, and of other nitrogenous com- 

(2) That the formation of cyanamid in the action of nitrogen 
on carbides must be due to an excess of nitrogen, which condition 
may take place from the time that this gas comes in contact with 
the carbide. 

(3) That the formation of cyanamid may be increased, by giving 
the carbide a greater surface, either by powdering it or by making 
it very porous and allowing the nitrogen to act, at a high tempera- 
ture, varying from a dull red to incandescence, upon a thin layer 
of carbide. In this case it will be easily understood that the con- 
ditions will be eminently favorable for the formation of cyanamid, 


a large quantity of nitrogen coming in contact with a small quantity 
of carbide. It is upon this series of remarkable observations that 
Frank and Caro have based their new patent, No. 289828, Oct. 2, 

Carbide, or a mixture of two or more carbides, or of a carbide 
with other salts of alkalis or alkaline earth, is subjected to the 
action of nitrogen or of ammonia under the conditions stated above, 
with the view of favoring the production of cyanamid and of its 

The substance thus obtained is then converted into cyanide by 
fusing it with alkali hydrate or carbonate, which may be added 
to the materials of the reaction before or during fusion. 

If the mass does not contain sufficient carbon, set free by the 
preceding reactions, it is well to add suitable quantities thereof. 

Likewise, if the materials to be treated contain compounds of 
nitrogen which are not combined to a metal, e.g. paracyanogen, 
it is necessary to add a sufficient quantity of a base in order to com- 
bine the cyanogen formed. 

This fusion results in converting the metallic compounds of 
cyanamid and of paracyanogen into cyanides corresponding to the 
bases used, according to the equations: 

(1) M 2 NCN+C = 2MCN and 


Generally the following are used: 

Oxid or carbonate .......................... 1 part 

Salt of cyanamid .......................... 2 parts 

It is best to treat the product of the reaction with water, then 
to displace the hydrocyanic acid by an acid, e.g. carbonic acid. 

The cyanamid remaining in solution is separated by shaking 
with ether or other solvent, or by other appropriate means. 

While studying the ammonia processes a process will be noted 
which, although it does not utilize the carbides, has for its object 
the production of cyanamid. The solution of the problem seems 
to be along this line. Frank and Caro's processes certainly de- 
serve to be kept in mind; they solve the problem quite satis- 
factorily and in an economic manner, seeing that the carbides are 


prepared with ease. We do not know whether these methods 
have been adopted on an industrial scale, though they were to 
have been tried in some Frankfort works. It was hoped that the 
experiments undertaken along this line would be crowned with 
success, since the use of carbides in the manufacture of cyanides 
would open, in fact, an important market for the former. 

Unfortunately, it would seem that the works at Frankfort have 
stopped operation, the results obtained not having been thought 
sufficiently profitable for their continuance. 

Other methods likewise based on the use of carbides have fol- 
lowed those of Frank and Caro. 

Process of the " Chemische Fabrik Pferse*e Augsbourg." In the 
first place comes this process (French patent No. 252943, Jan. 3, 1896; 
English patent 1022, Jan. 15, 1896). It consists in allowing free 
nitrogen at a red heat to act upon a mixture of calcium carbide 
(or barium carbide) and dry alkali carbonate. 

According to the investigators there would first be established 
a reciprocal reaction between the alkaline-earth carbide and the 
alkali carbonate, which in the case of calcium carbide and potassium 
carbonate may be thus expressed: 

CaC 2 +K 2 C0 3 = C 2 K 2 +CaO+C0 2 ; 

the carbonic acid would be immediately reduced to the state of 
carbon monoxid by means of a small amount of calcium carbide 
in excess. 

The potassium carbide formed would then absorb the nitrogen 
according to the equation 

C 2 K 2 +2N=2CNK. 

The reaction takes place still better in the presence of ammonia : 
C 2 K 2 +2NH 3 =2CNK+6H. 

The inventors propose to apply this property of the carbides 
to the old process of manufacture, which consists in using alkali 
carbonates, organic animal substances, or nitrogenized charcoal, 
and to ignite the whole at a high temperature. By adding a car- 
bide to these substances the reaction would take place at a lower 


temperature than that thought necessary up to the present time 
and the yield which was relatively small would be increased. 

The advantages which would follow from the process of the 
Chemische Fabrik Pfersee Augsbourg would be the following: 

(1) An appreciable decrease in the cost of fuel, and wear and 
tear of the apparatus due to the relatively lower temperature of 
the reaction. 

(2) The easy and abundant absorption of nitrogen. 

(3) The obtaining, under the form of cyanides, of the almost 
theoretical quantity of ammoniacal nitrogen used. 

These last two points should be verified industrially. 

Beringer's, Wolfram's, and Blackmore's Processes. Among the 
other methods using carbides must be mentioned that of Beringer 
(German patent 20334, Feb.-Nov., 1897), which consists in passing 
nitrogen over carbides, noting that the conversion into cyanides is 
complete at 900, if dry and pure nitrogen be used, a condition 
which would complicate the solution of this problem from an indus- 
trial standpoint (the inventor claims that the reaction begins even 
at about 450 C.). 

Wolfram's method (1898) consists in causing a metallic carbide 
(alkaline?) and a nitrogenous compound or free nitrogen, preferably 
ammonia, to act upon an alkali hydrate in state of fusion. 

Blackmore's method (U. S. patent No. 605694, June, 1898) seems to 
complicate instead of simplifying matters. The inventor proposes 
to compress the nitrogen into a mixture of alkali sulphide and metallic 
carbide, preferably carbide of iron. The sulphide becomes converted 
into the corresponding cyanide, more or less contaminated with ferro- 
cyanide and sulphocyanide, according to the amounts of the charge 
and the conditions of the reaction, conditions which are, moreover, 
not stated in the patent. Besides, the complete purification of 
this product must be rather expensive, and the author of the patent 
refrains from stating what is necessary in order to bring it about. 
This process, which is of little value, does not deserve deep study. 

Dziuk's Process. Very interesting, however, is the method of 
Dziuk (French patent No. 286828, March 15, 1899). 

Dziuk of Hanover uses the alkaline-earth carbides, as do Frank 
and Caro, not, however, at the temperature of redness but at that 
of igneous fusion 01300-3000), the nitrogen also being previously 


heated at a high temperature. This modification is based on the* 
fact that nitrogen acts on the alkaline-earth metals and on mag- 
nesium only at a very high temperature. This fact led the author 
to believe that nitrogen likewise should act on the carbides only 
at a temperature at which their constituent elements are in a free 
or nascent state. And, in fact, he was able to observe that if a 
current of nitrogen, heated to a high temperature before coming 
in contact with the carbide, be made to pass over calcium carbide 
manufactured in an electric furnace, this latter substance is con- 
verted into cyanide so long as it remains in the liquid state. 

Here is how Dziuk in his patent explains this phenomenon. 
The nitrogen is first absorbed by the metal yielding a nitride which 
uniting with free carbon forms cyanide. 

In practice, Dziuk uses any kind of electric furnaces which is 
used in the manufacture of carbides. Into the fusion chamber f 
at right angles to the electrodes, opposite the charcoal tube enclosing 
the fusion mixture, he introduces a second charcoal tube which 
serves to conduct the atmospheric nitrogen which has been care- 
fully freed from carbonic acid, moisture, and oxygen, and which 
has been highly heated. 

Thus, a brown-colored product is obtained which is composed 
almost entirely of cyanide and contains but a minimum amount 
of unconverted carbide. It appears best to allow the mass to cool 
somewhat in the nitrogenous atmosphere of the furnace. 

Carbide in the process of formation in the electric furnace may 
be used or else carbide already formed, which however must first 
be subjected to fusion. This process is applicable to all the alka- 
line-earth carbides and to magnesium carbide, likewise to a mix- 
ture of these carbides. 

These gases which issue from the furnace may be used in heating 
the nitrogen, and the cyanides obtained may be converted into alkali 
cyanides by double decomposition. 

Dziuk comes to the same conclusion in an improvement to this 
patent by heating magnesium or lime in an electric furnace under 
the action of a current of nitrogen, then adding carbon in the form, 
of coke in small portions. All this without interrupting the 
current. Under these conditions there is first formed a nitride 
which the carbon converts into cyanide. 


Process of the General Electrochemical Co. The last process 
to be mentioned, which makes use of carbides, is that of the Gen- 
eral Electrochemical Company (French patent No. 299655, April 24, 
1900). Like Dziuk's method, this process consists in causing nitrogen 
to pass over carbides in an electric furnace, but with this differ- 
<ence that the carbides are prepared in a special manner so as to 
make them more porous, and therefore more permeable and of 
greater surface for the action of nitrogen. 

To attain this state of porosity, coke is added to the carbide 
which renders it more fusible, or else the carbide is prepared with 
.an excess of carbon. 

In practice, the following is the method of procedure: granu- 
lated carbide is mixed with coarsely ground coke and the mixture 
introduced into the incandescent electric furnace. The presence 
of this coarse coke brings the charge into a state of porosity which 
is very favorable to the absorption of nitrogen. The carbides of 
the bivalent elements are particularly suited to this purpose, for 
they are unsaturated compounds, each carbon atom having four 
chemical affinities, two of which may be united to a bivalent alka- 
line-earth metal, leaving ^jreg^free affinities to each carbon atom. 
With these compounds it is quite easy to pass from the unsaturated 
to the saturated state by adding new elements having the smallest 
number of satisfied affinities. If nitrogen be passed through a 
heated mass of porous carbide, each molecule of carbide absorbs 
two atoms of nitrogen in order to become saturated, the three affini- 
ties of each carbide molecule being replaced by the three affinities 
of each of the two atoms of nitrogen, it being understood that car- 
bon has a greater affinity for nitrogen than for itself. 

The best way to obtain carbide porous enough for the manu- 
facture of cyanides consists in mixing and pulverizing barium 
carbonate with an amount of coke greater than that necessary 
for the manufacture of barium carbide. The most convenient 
proportions to use are 3 parts of barium carbonate and 2 parts soft 
coal. This mixture is subjected to carboniziation in an ordinary 
retort furnace. The result is a porous mass of coke in which the 
barium carbonate is found firmly fixed to the cellular walls. 

This mass is transferred to an electric furnace which rotates 
-continuously and subjected to a sufficient heat to produce barium 


carbide. This substance fuses on to the particles of coke present 
in excess, forms a porous carbide, which afterwards easily absorbs 
the nitrogen at a temperature below that of the fusion of the car- 
bide, yielding a cyanide of barium which may be separated by solu- 
tion and crystallization. 

Such are the synthetic processes which utilize atmospheric nitro- 
gen. As may have been noticed, the progress achieved along this 
line has been remarkable. Of all these methods, five or six only 
deserve to be kept in mind, viz.: those of Lambilly, Margueritte, 
Sourdeval, Castner, and those of Frank and Caro, Dziuk, and of 
the General Electrochemical Company. It is very doubtful if 
the others can be profitably exploited. 


Nitrogen being such an inert element, and its fixation being 
often laden with difficulties, it was sought to utilize ammonia whose 
chemical activities are much greater. 

Liebig was one of the first to show that the ignition of nitroge- 
nous organic substances in the presence of an alkali forms ammonia 
which in contact with charcoal heated to incandescence becomes 
converted into ammonium cyanide. Upon these data are based 
the processes of Karmrodt, Lucas, and Brunquell for the profitable 
conversion of animal substances into cyanides. 

To Scheele, however, belongs .the credit of having shown that 
ammonia may contribute to the formation of potassium cyanide. 
Scheele had even invented a proce s based on this observation and 
which consisted in heating a mixture of ammonium chloride, char- 
coal, and potassium carbonate. 

Somewhat later Clouet demonstrated that when ammonia was 
passed over incandescent charcoal a soluble substance was obtained 
having a bitter-almond taste, and which in all probability was 
ammonium cyanide, according to the reaction 

Langlois likewise obtained a similar result, and noticed the 
formation of small prismatic crystals of ammonium cyanide. 

When a mixture of carbon monoxid and ammonia was passed 
over platinum sponge heated to redness, Kuhlmann likewise con- 
firmed the formation of ammonium cyanide. 


Weltzien also obtained a similar result. All these investigations 
are but laboratory experiments, and the investigators often found 
themselves opposed to one another; nevertheless to them belongs 
the credit of creating experiments on an industrial scale. More- 
over, the question is still obscure enough. In 1897 Bueb and 
Bergmann demonstrated that when ammonia acts On incandescent 
charcoal there is formed not ammonium cyanide but hydrocyanic 
acid, according to the equation 

C 2 +2NH 3 ^2CNH+2H 2 , 

while according to Lance (Comptes Rendus, April, 1897) the prod- 
uct of this reaction is always ammonium cyanide. 

In the course of his experiments on the action of ammonia on 
charcoal at different temperatures, Bueb showed that at 800 the 
formation of hydrocyanic acid is quite small, i.e. about 4% of the 
nitrogen used; that at 1000 the yield increases to 24%, but from 
this temperature on the rest of the ammonia becomes dissociated. 

He noted that the result was quite different when a mixture of 
ammonia and illuminating-gas was used instead of ammonia alone. 
In that casb, even at 1150-1180, three fifths of the nitrogen of the 
.ammonia are converted into hydrocyanic acid, one fifth of the am- 
monia is obtained as hydrogen and nitrogen from the dissociation 
of the ammonia, and the remainder is not dissociated. 

Repeating Bueb's experiments, Bergmann came to the following 

1. The action of ammonia on charcoal heated to redness gives, 
indeed, hydrocyanic acid, and not ammonium cyanide. 

2. The addition of illuminating-gas to ammonia causes an 
increased yield of hydrocyanic acid and increases the resistance of 
ammonia to dissociation. 

By working with a gaseous mixture containing 8-14% ammonia 
by volume, at a temperature between 1100 and 1180, Bergmann 
observed that 19-52% of the nitrogen was used and converted into 
hydrocyanic acid, 69.2 to 19% was found in the state of ammonia, 
and 11 to 41% as free nitrogen. Moreover, the yield varies in 
inverse ratio to the velocity of the gases. 

3. If, instead of illuminating-gas, hydrocarbons of higher molecular 
weights be used, the yield of hydrocyanic acid is not increased but 



rather diminished, which fact seems to prove that nascent carbon 
has no action on ammonia. 

4. If the illuminating-gas be replaced by carbon monoxid, the 
yield is about the same, but the amount of dissociated ammonia 
is greater. 

Below are the results obtained by Bergmann. 

Duration of 


Per Cent NH 3 
by Volume. 

Per Cent of N 
used in Form 
of CNH. 

hr. niiu. 









1 20 
















1 35 








1 6 




5. The increase in the yield of hydrocyanic acid, confirmed 
in the experiments made with mixtures of ammonia and carbon 
monoxid or illuminating-gas, is not due to the chemical action 
exerted by this gas, as one would be led to believe, according to 
the equation 

CO+NH 3 = CNH+H 2 0, 

but it is the result only of the dilution of the ammonia-gas. In 
fact, in many experiments made with carbon monoxid and ammonia 
without the intermediary of wood charcoal, Bergmann proved 
that only 0.4 to 0.6% of the nitrogen used in the form of ammonia 
wac converted into hydrocyanic acid, 32.5-62.2% was found as 
ammonia, and 34-68% in the form of free nitrogen. 

6. The most favorable temperature for the formation of hydro- 
cyanic acid depends materially on the nature of the gases used in 
diluting the ammonia. It is from 1000 to 1100 for carbon monoxid, 
generator gases, and mixtures of hydrogen and nitrogen; 1100 at 
least for the various gaseous hydrocarbons. At this temperature 
the dissociation of the ammonia decreases as the molecular weights 
of the hydrocarbon increases. 


Compared with the results of Bergmann those of Lance present 
Striking analogies, while at the same time differing considerably. 

While studying the action of ammonia-gas on charcoal heated 
to redness, Lance observed (Comptes Rendus, April, 1897) that 
if dry ammonia-gas be passed over wood charcoal at the rate of 
four liters per hour, at a temperature between 1000 and 1100, 
(1) ammonium cyanide is always formed; (2) the yield is great- 
est at this temperature; (3) the nitrogen combined under this 
form is equal to 25% of the nitrogen used under the form of 

If the ammonia-gas be diluted with hydrogen and nitrogen, the 
results are quite different. 

1. If the ammonia constitutes I /Q of the gaseous mixture, the 
yield in nitrogen converted into cyanogen in increased to 30.6%. 

2. This yield increases with the increase of the quantiy of hydro- 
gen in relation to the nitrogen, and may react 89.66% if the nitrogen 
constitutes but 1 /io of the volume of hydrogen. 

3. Under these conditions at least 70% of the nitrogen of the 
ammonium cyanide comes from the free nitrogen of the mixture, i.e., 
from the nitrogen of the air. 

From these results, which are similar and yet contradictory, 
the conclusion reached is that the action of ammonia-gas alone, 
or mixed with other gases, on incandescent charcoal, is not at all 
well known. It requires still considerable study. Probably the 
action of the carbon is only one of contact, as is the case in many 
chemical reactions. This hypothesis is all the more probable if 
one recalls how Bergmann was able to obtain only traces of cyanogen 
by the action of nitrogen on carbon monoxid in the absence of char- 
coal, and, on the other hand, Kuhlmann obtained appreciable quan- 
tities of ammonium cyanide by working with the same gases, but 
in the presence of platinum sponge heated to redness. Be that 
as it may, these investigations have been the point of departure 
of several processes based on the action of ammonia upon incan- 
descent wood charcoal. 

Lance and Bourgade's Process. First comes the method of Lance 
and Bourgade (French patent No. 265932, 1897). In this process 
ammonia is used only as the carrier of hydrogen and nitrogen. Under 
the name hydrogen the authors mean all the gaseous hydrocarbons, 


gas, water, etc., and by nitrogen is meant either pure nitrogen or 
in the form of mixtures, such as air and the products of combustion 
of manufacturing establishments. 

This process is based on the following reactions: If a mixture 
of acetylene and nitrogen be made to act upon one another in the 
presence of intense heat, there is formed hydrocyanic acid. The 
richer the mixture is in hydrogen, the nearer to the theoretical 
yield is the amount of hydrocyanic acid. It is at a maximum when 
the volume of hydrogen is at least two and one half times that of 
the hydrogen combined in acetylene. 

If therefore a mixture of nitrogen, hydrogen, and ammonia be 
passed over carbon, there is formed an acetylene carbide of ammo- 
nium, C 4 (NH 4 )2, which is only a transition product with which free 
nitrogen combines, yielding the compound C 2 N-NH 4 or ammonium 
cyanide : 

2NH 3 +2H+4C = 

C 4 (NH 4 ) 2 +2N=2(C 2 N.NH 4 ). 

The yield approaches the theory in proportion as the conditions 
stated above relative to the mixture of the three gases, nitrogen, 
hydrogen, and ammonia, are adhered to. In their German patent 
No. 100775, taken Aug. 22, 1897, Lance and Bourgade give the 
following proportions : 

Ammonia-gas ........................... 80 liters 

Hydrocarbon ........................... 2000 ' ' 

Nitrogen of air .......................... 200 ' ' 

The ammonium cyanide obtained is then treated by well-known 
and appropriate methods to convert it into alkali cyanide. 

Mactear's Process. This is a somewhat similar process (U. S. 
patent No. 654466, July 24, 1900, French patent No. 292639). It 
consists in passing a mixture of carbon monoxid and ammonia-gas 
through a specially constructed chamber filled with wood char- 
coal or other suitable catalytic substance heated to 1800-2000 
by means of electrical resistances. 

The mixture of the two gases is previously made in a closed 
chamber in the proportion of two volumes of ammonia-gas and 


one volume carbon monoxid. This gaseous mixture is then con- 
ducted through the decomposition chamber. The carbon monoxid 
should be pure; it is produced by passing a current of carbonic 
acid over coke heated to redness. The ammonia is obtained by 
the decomposition of ammonium sulphate with lime. 

The gaseous products consist, for the most part, of ammonium 
cyanide. This latter product is then converted into alkali cyanide 
by treating it with a corresponding amount of alkali hydrate in 
a water or alcoholic solution. 

The ammonia of the ammonium cyanide is set free and collected 
the solution of alkali cyanide is then evaporated. 

Process of the Stassfurter Chemische Fabrik. This process 
belongs to that class which utilizes the reaction of ammonia on 
charcoal. It is based on the following facts: When a current of 
ammonia is passed over a mixture of alkali or alkali carbonate and 
charcoal heated to dull redness, there is formed, indeed, a cyanide, 
but only in small amount, whereas a considerable amount of cyanate 
is produced. 

The result is quite otherwise if the ammonia-gas be conducted 
through at a dull-red heat, and if after this adduction has ceased 
the heat is increased to full redness; the cyanate at first formed 
is reduced to alkali cyanide. 

Gruneberg, Flemming, and Siepermann have patented a cyanide 
furnace (German patents Nos. 38012, 1886; 51562, 1889; French pat- 
ent No. 200492, 1889) which has precisely the object of utilizing 
these reactions. 

The manufacture of cyanide takes place in two stages in vertical 
retorts, several of which are placed in the furnace and comprising 
many parts; one part is heated to dull redness where the cyanate 
is formed, the other part heated to full redness where the cyanate 
is reduced to cyanide. 

These retorts, A (Figs. 6 and 7), are enclosed in the furnace B 
with flues and placed in such a manner that the lower part of them 
is heated to an intense red, while the upper part is heated to a dull 
red. The lowest part of the retorts, C, is situated outside the fur- 
nace. It serves as a cooler for the cyanide formed, which is then 
collected in the receiver D, whence it is carried off by an endless 
canvas E. The mass, which is to be converted into cyanide, com- 



posed of bits of wood charcoal impregnated with potassium car- 
bonate , falls in virtue of its own weight from that part the least 
heated into that part which is heated to intense redness. It is 
introduced through the hoppers FF, which are afterward closed. 

FIG. 6. Apparatus of the Stassfurter Chemische Fabrik 

As soon as the desired temperature has been reached, the tube G 
is pushed so as to bring about the lower opening at the point where 
the dull-red zone begins. 

Then a carefully regulated current of ammonia is allowed to 


pass through. The products of the reaction fall slowly into the 
receiver D and are carried off by the endless canvas E. The hop- 
per F is filled at regular intervals. The gases, set free during the 
reaction, go out through the tube H, in whose axis is the tube G con- 
ducting the ammonia. A revolving drum, J, situated in the lateral 
flues of the furnace and heated by the flames escaping from the 
latter, permits the charge to be dried beforehand, for it should not 
be used in a moist state. The mass obtained is systematically 
treated with water until the solutions show a specific gravity of 
40 B. The liquor is then treated with carbonate of potash either 

FIG. 7. Apparatus of the Stassfurter Chemische Fabrik. 

at ordinary or at a higher temperature. The greater portion of 
the potassium cyanide separates immediately if the work be carried 
on at ordinary temperatures, or crystallizes on cooling if carried 
on at a higher temperature. 

The Stassfurter Chemische Fabrik, formerly Forster & Grune- 
berg, which has installed this process in its works, has at the 
present time 52 such furnaces, * which are regularly operated, 
and which, it seems, give splendid results. It would appear that 
negotiations were in progress last year between a French com- 
pany and the German company for the installation of this process 
in a chemical works near Paris. 

Moulis and Sar's Process. This process (French patent No. 
265715, March 26, 1897) likewise makes use of the action of ammo- 
nia on charcoal. The necessary ammonia is produced from the 
nitrogen of the air in the following way: 


Air under pressure is blown into a vat-like furnace containing 
a certain quantity of small pieces of wood charcoal or cinders of 
coke. First there is formed carbonic acid, which passing through 
the red-hot charcoal of the upper zone is converted into carbon 
monoxid. This oxid of carbon, together with a small amount of 
carbonic acid and undecomposed air, passes before a reservoir of 
air so placed that this air becomes thoroughly mixed with the oxid 
of carbon so as to produce its complete combustion. In this way 
a mixture of nitrogen and carbonic acid is obtained together with 
a considerable amount of calories which may be used in heating 
the apparatus. The carbonic acid is absorbed by potash or sodium 
hydroxide and the nitrogen stored in a gasometer. 

On the other hand, hydrogen is produced according to well- 
known methods (zinc and acid of 20 B.). When this hydrogen 
passes through nitrogen, at suitable temperatures, ammonia is 
formed. This latter gas passes through a refractory tube heated 
by means of oxid of carbon, and into which dehydrated and liquefied 
tar flows. Under these conditions the tar is vaporized, the vapors 
coming in contact with the ammonia and forming ammonium cya- 
nide, which is collected in water and afterward converted into alkali 

The action of ammonia (substituted for nitrogen) on the oxids^ 
carbonates, and metals of the alkalis, in the presence of charcoal, 
has likewise been tried. The processes of this kind are quite numer- 
ous and will now be passed in review. 

Lambilly's Process. Lambilly, whose remarkable researches 
have been discussed at the beginning of this chapter, is one of 
the first to have tried, with some success, to replace nitrogen, 
either partly or wholly, by ammonia. Having remarked that the 
reactions were conducted with greater ease if the carbon was in 
the nascent state, Lambilly thought that this advantage would 
be still more manifest if the nitrogen also was in this state, and 
with this end in view he proposed to substitute, partially or wholly, 
the nitrogen with ammonia. In his French patent (No. 223868, 
Aug. 26, 1892) he works as follows: He uses a mixture of hydro- 
carbon-gas and ammonia-gas with the optional addition of free 
nitrogen. This mixture is decomposed at a high temperature in 
the presence of an alkali or alkaline-earth compound and charcoal. 


The cyaniding mixture is obtained in the following way: A con- 
centrated solution of carbonate of potash or caustic potash or caustic 
Boda is made, into which is poured pulverized charcoal at the rate 
of 100 parts per each 100 parts alkali. This mixture is evaporated to 
dryness, then to it are added 20-30 parts powdered lime and 50 parts 
iron filings, and the whole is massed together into the form of bri- 
quettes with the aid of tar or other like substance. These are then 
ignited in iron retorts or cylinders heated to bright redness in 
such a way as to reduce as much as possible the alkali compound 
and to convert it into a state favorable for the absorption of nitrogen. 
This operation is best carried on in a vacuum. When this is fin- 
ished, this point being indicated by the cessation of the liberation 
of gas (H 2 or C0 2 ) according to the alkali compound (hydrate 
or carbonate) used, the gaseous mixture of ammonia and hydro- 
carbon with or without free nitrogen is made to pass through. 
The latter gas is produced by passing air over copper heated to 
redness, and the oxid of copper formed serves in carbureting the 
hydrocarbon-gas. This hydrocarbon-gas should preferably be quite 
dense. It may be profitably obtained by heating charcoal impreg- 
nated with heavy coal-tar oil in cylinders at a temperature between 
50 and 300. 

The gaseous mixture passes over the cyaniding substances under 
a slight pressure, in order to bring it into intimate contact with 
all the particles of this substance. On issuing from the retorts the 
gases are recarbureted. The mass so obtained is withdrawn from 
the cylinder and treated with water. In the claims of his patent 
Lambilly states the following advantages of his process: 

1. A great rapidity. 

2. It permits, in a single operation in a definite amount of 
alkali, the amassing of more cyanide than any other process at 
the time known. 

3. It is therefore very economical. 

Beilby's Process. This process, dating from the same year 
(French patent No. 219156, Feb. 4, 1892), does not present any great 
improvement over the processes then known, and besides the net 
cost must be quite high. It consists in passing a current of ammonia 
through a melted mixture of anhydrous caustic alkali, cyanides^ 
and finely powdered charcoal heated at a high temperature in a 


suitable apparatus. The addition of cyanide is to lower the point 
of fusion of the mass, in order to avoid deterioration of the iron 
receptacles in which the operation is conducted. 
The amounts stated by Beilby are: 

Pulverized charcoal 20 to 25% 

Potassium carbonate 55 " 60% 

Potassium cyanide 20% 

The apparatus used are retorts or pots of iron provided with 
a tube for the inlet of ammonia, an outlet tube, a hopper, and a tap- 

The ammonia may bubble through the melted mixture, or else 
the mixture may be subjected to an energetic stirring by means 
of a mechanical stirrer during the passage of the current of am- 

It is important always to have some potassium cyanide in the 
mixture during the operation, and in such amount that the mass 
remains fluid, without, however, producing foam, which might 
obstruct the exit. 

The cyanide which in part is volatilized is collected in a system 
of condensers. The operation may be so conducted that the whole 
of the cyanide is volatilized. Ammonia may be substituted by 
the alkaloid bases of the pyridine series. 

As was remarked, this method must be rather expensive because 
of the amount, 1 / 5 , of cyanide added to the other products. 

The substitution of the alkaloid bases for the ammonia is not 
profitable. Besid s being expensive bodies, they are quite resistant 
to high temperatures and an appreciable amount of these bodies 
thus escape decomposition,. 

Young and Macfarlane's Process. The method of Barr, Mac- 
farlane, Mills, and Young (English patent No. 3092, 1892; French 
patent No. 230066, May 13, 1893) is somewhat different. It is based 
on the action of a mixture of ammonia and carbon monoxide on a 
fused mixture of alkali hydrate or carbonate and charcoal, accord- 
ing to the general reactions: 


H-CO-NH 2 = 
2CNH + C0 3 K 2 + C = 2CNK + H 2 + 2CO. 

The most suitable proportions are: 

Caustic potash ...... ................... 100.0 parts 

Charcoal (wood charcoal or coke) ......... 22.5 " 

This mixture is heated at 815 C. in a retort or other receptacle, 
then a current of carbon monoxid and ammonia is passed through, 
either separately or previously mixed, and heated if thought necessary. 
Under these conditions there is formed a cyanide corresponding 
to the base used, which may afterward be separated and purified 
according to ordinary methods. The gases which come out of 
the retorts may be used over again after being enriched with the 
one or other necessary constituent. 

As a profitable source of ammonia and carbon monoxid, the 
authors recommend using the gases of blast-furnaces or other indus- 
trial furnace gases, likewise gases from slate-retorts or from gas- 
works, after purification, if they are thought suitable. 

Under these conditions the authors claim a yield of 70%. Repeat- 
ing the experiments of Young and Macfarlane under the most favor- 
able conditions, Conroy was able to obtain a yield of but 30%. He 
remarked, besides, that the cyanide is formed very slowly, Mac- 
farlane himself has, moreover, stated that 36 hours are required 
to produce a yield of potassium cyanide of from 60-70%. The 
longer the experiment continues, the more rapid becomes the for- 
mation of cyanide. This method, moreover, requires an elevated 
temperature, which causes a rapid wear and tear of the apparatus. 
Thus, in Young and Macfarlane's experiments, the steel tube which 
was used in carrying on the reaction was reduced, at the end of 
36 hours, to the thickness of an ordinary sheet of paper. Conroy 
repeated the experiment with a cast-iron tube and noted a similar 
wear. According to him the reaction would take place as follows: 

NH 3 +KOH=KNH 2 
KNH 2 + CO = CNK + H 2 0. 


According to the authors of the patent there would be formed 
formamide, which would then break up into water and hydrocyanic 
acid, which latter would be absorbed by an alkali. 

Conroy's hypothesis presupposes the formation not of formamide, 
but of potassamide. According to his idea, the formation of cyanide 
is due rather to a simultaneous action of the three substances pres- 
ent, and probably with the formation of potassamide as an inter- 
mediary product. Moreover, Beilsten and Geuther had previously 
established the fact that the oxid of carbon reacts on the potassa- 
mide with formation of potassium cyanide. Repeating this experi- 
ment by heating potassamide in a glass tube at 50-600 under the 
action of a current of carbon monoxid, Conroy was able to obtain a 
yield of 35% potassium cyanide. He considered, however, that 
if instead of a glass tube he had used an iron tube, the yield would 
have been almost theoretical. Without deciding in favor of either 
one or the other of these two suppositions, both equally established, 
it will be seen further on that the latter seems more probable, judg- 
ing from the results recently obtained with a new process the object 
of which is the intermediary production of alkali amides. Never- 
theless, since these data have not yet been confirmed experimentally 
we will rely on the results obtained. 

Chaster 's Process. This process (1894) does not present any- 
thing very new or characteristic. It simply consists in passing 
ammonia which has been previously dried over quicklime, over 
an intimate mixture of coal and a carbonate of an alkali or alka- 
line earth. As in Lambilly's process, this mixture is prepared by 
adding powdered coal to a concentrated solution of carbonate, 
evaporating to dryness, and igniting. 

Pleger's Process. This process (German patent, No. 89594, Aug. 
7, 1895) also does not differ much from the preceding ones. It 
consists likewise in causing a current of ammonia to act on a mix- 
ture of alkali and charcoal heated to 900. The author, however, 
does not add at once the whole of the charcoal necessary. Only 
a portion of it is used, the rest being carried in gradually with the 
ammonia-gas which is blown into the crucible. Ammonia charged 
with pulverized charcoal is continually blown in until there is no 
longer any liberation of hydrogen or of carbon monoxid. When 
this point has been reached the mass is allowed to remain in quiet 


I fusion, and the melted cyanide is filtered in order to separate it 
| from the excess of charcoal. As in all the preceding processes of 
I this class, the ammonia may be replaced by nitrogen, either of the 
[ air or in the form of the mixture which the local combustion of 
1 carbon in excess produces. 

These various processes, which are more or less similar, pro- 
duce greater or Jess amounts of cyanide, the yield, however, never 
being equal to the theoretical, and Conroy estimates, and not with- 
out reason, that 2 /3 are lost. One of the causes of this failure is 
to be found in the resistance which the cyaniding mixture presents 
to the action of ammonia-gas. Now, one of the essential condi- 
tions of success is that the mixture allow the gaseous current to- 
circulate freely while being intimately penetrated by it. 

Roca's Process. Roca in his French patent No. 266550, May 3, 
1897, seems to have realized this desideratum. For this purpose 
he first brings his cyaniding mixture to a special physical condition 
of porosity, which is especially suited to assure the most perfect 
and most economical absorption and circulation of the ammonia 
throughout the mixture and its transformation proceeds into 

Roca starts with the idea that this mixture should not be so 
fine as dust, but rather in small pieces which will leave spaces between 
each other large enough to allow the circulation of the gas and 
permeable enough to this gas that the action will not be confined 
to the surface. Moreover their weight should not be such as to 
cause the pieces to become crushed, and therefore they should main- 
tain a certain degree of hardness. 

Toward this end he mixes finely ground wood charcoal, ground 
in the presence of water so as to lay the excessive dust, with the 
purest commercial potassium carbonate in the proportion of 30-35 
parts of charcoal t,o 65-75 parts carbonate.' He adds 10-20% water 
so as to make the mass homogeneous and slightly moist. Thus 
prepared, this mixture when squeezed in the hand should form 
a soft ball. 

This mass is then spread out and pressed into thin layers upon 
a metallic floor capable of being heated. The potassium carbonate 
dissolves in the small amount of water contained in the mixture and 
then it imbibes the charcoal, the whole forming an intimate mass. 


The mass then becomes turgid and coherent, and under the influence 
of heat the small quantities of air and water-vapor seek to escape, 
leaving small cavities in the interior of the mass. Finally, after 
drying completely, there is obtained a sufficiently hard charcoal,, 
which resists being crushed, which is very homogeneous, porous, 
and at the same time of very low specific gravity (density 0.45 
0.55), and which may be cut up into briquettes. This mass is kept 
out of contact of air and moisture until it is to be used. 

This mass is charged into vertical cast-iron retorts which are 
hermetically covered and provided at the lower part with a vane, 
forming an air-tight joint during the cyaniding process. It is only 
necessary to open this vane to make the cyanided product flow into 
a sheet-iron extinguisher. 

These retorts are arranged in series of five or six in suitable 
furnaces. Each retort is provided with two tubulatures. One, 
placed near the cover, serves to admit the gases; the other, placed 
a little above the vane, serves as their exit. The bottom of the 
retorts are covered with pieces of dry wood charcoal so arranged 
as to avoid any incomplete transformation on account of lack of 
heat and to facilitate the exit of gases. 

Uniform circulation and continuity of working are made sure 
by a system of pipes and suitable valves (see Fig. 8). 

The arrangement shown in Fig. 8 permits one to understand the 
principle of the apparatus and the workings of the various taps. 
According to the cut, ammonia-gas is admitted into the apparatus 
by way of tap 7 3 in the retort C 3 , which is the one earliest charged; 
it passes into retort C 2 by means of Z 2 , and into retort d through 
XL From this retort the gas goes through the tap X 5 into <7 5 , 
and through X 4 into C 4 ; then it flows into the exit tube through 
the tap F 4 . Every time a retort is cyanided, the order of using 
the cocks is changed and thus a continuous operation is permitted. 
By means of this arrangement any one of the retorts may be dis- 
connected during the unloading and reloading without stopping 
the operation in the other retorts. 

In this way a mixture of nearly pure cyanide and charcoal is 
obtained which, after cooling, may be treated with water and puri- 
fied in the usual way. The residual charcoal, when well washed, 
may be used anew. 


The gases which are discharged from the furnace are cooled 
and are then conducted into a tower filled with coke, where a thin 
stream of water circulates and holds back the entrained ammonia. 
Thence they are conducted under the hearth and used as fuel, for 
they liberate more heat than is absorbed by the endothermic reac- 
tion obtained in the retorts. In this way the expense of fuel is 
considerably lessened, and in fact it is, on this account, very small. 

Tnlet for Ammonia- 

Qutlet-tor Gas 

FIG. 8. Roca's Apparatus (plan). 

In an addition to his patent, Roca advises the substitution of 
barium carbonate instead of potassium carbonate, and this for several 

The cyanide obtained is very soluble and chemically pure, the 
barium carbonate being insoluble and not passing into the cyanide 
solution when the cyanide is treated with water. 

Barium carbonate is not so expensive and it may be regenerated 
when the barium cyanide is converted into alkali cyanide. More- 
over, at the temperature at which the reaction takes place (800- 
900), carbonate of barium dissociates much less than does carbo- 
nate of potassium, and almost no soluble baryte is formed to con- 
taminate the cyanide. 

The cyaniding mixture is formed by mixing 100 parts of the 


purest commercial carbonate of barium with 30-35 parts wood char- 
coal. Then are added 20-25 parts of a dilute and warm solution 
of gelatine in order to make the mixture cohere. After drying, 
the mixture is broken up into pieces of the desired size, and these 
are transferred to the apparatus described above and treated in the 
same manner. 

The product thus obtained is treated with water, and after fil- 
tration the barium cyanide is converted into an alkali cyanide 
by the addition of an alkali carbonate according to the following 
reaction : 

(CN) 2 Ba+C0 3 K 2 or C0 3 Na 2 =C0 3 Ba+2CNK or 2CNNa. 

soluble soluble insoluble soluble 

The precipitated barium carbonate is separated by filtration, 
and after drying, it may be used anew. 

As may be seen, Roca's process is really ingenious, and it shows 
a marked improvement over all the preceding processes. Yet it is 
very doubtful if by this process, even, a theoretical yield can be 
obtained, a condition which is extremely difficult of fulfilment when 
the oxids or carbonates of the alkalis are used. 

Hood and Salomon's Process. Before taking up the study of 
processes working directly on the alkali metals themselves, which 
to our mind simplifies the solution of the problem very much, we 
cannot omit mentioning the very original and peculiar process of 
Hood and Salamon (German patent No. 15142, 1895-1896). 

This process differs from the preceding in that it is worked not 
in the dry way but in the wet way. In an early patent (English 
patent No. 87613, Sept. 4, 1894) Hood and Salamon worked in the 
dry way. The alkali carbonate was treated with a reducing metal 
zinc, lead, etc. and this mixture was heated to redness in a cur- 
rent of dry ammonia. The reaction is as follows: 

NH 3 + C0 3 Na 2 + Zn = CNNa + NaOH + ZnO + H 2 O, 

but only half of the alkali metal is converted into cyanide. In 
order to complete the reaction profitably the authors proposed 
that a current of heated carbonic acid and ammonia be passed 


over the mixture, or that a bit of charcoal be added to the mass 
in order to reduce the cyanate formed as well as the oxid of 

2Zn+C0 2 , 
2NaOH+C0 2 =C0 3 Na 2 +H 2 0. 

In the German patent (No. 15142, 1895-1896) Hood and Sal- 
amon operate in the wet way. If metallic zinc be in suspension in 
strong alkaline solutions to which carbonates or bicarbonates have 
been added, and a current of ammonia be passed through these 
boiling lyes with constant agitation, there is produced under 
these conditions alkali cyanide according to the same reaction 
as above. 

As in the case in the dry way, only one half of the alkali is 
converted into cyanide. The reaction may, however, be com- 
pleted by the addition of finely divided charcoal, which reduces 
the zinc oxid and carbonates to an equivalent quantity of alkali. 
The cyanide solution is then evaporated to dryness in suitable 

We do not know what results have been produced by this really 
peculiar process. One may truly ask oneself if the reactions do 
in reality take place as the authors state, and if the charcoal can 
really reduce zinc oxid under the conditions mentioned. These 
are points which require elucidation in order that this original 
method may be judged. 

The disadvantages inherent to the use of the oxids or carbonates 
of the alkalis or alkaline earths for their conversion into cyanides, 
and to which we called attention when the processes utilizing free 
atmospheric nitrogen were studied, reappear in the ammonia proc- 
esses using these same oxids or carbonates. The most serious of 
all, as we have seen, is the necessity of producing the high tem- 
perature required in the reduction of the compound used. 

As in the processes using nitrogen, it was sought to remedy 
this by making use of the alkali metals themselves. 

Hornig's Process. The first process of this kind is that of Hornig 
(German patent No. 15467, April 5, 1894; Feb. 21, 1895). This 


process deserves to be mentioned especially on account of its original- 
ity. It consists in making the vapors (?) of the alkalis or alkaline- 
earth metals (?) (which are produced in a separate generator) act 
upon carbon in the presence of nitrogen or ammonia, or upon com- 
pounds of nitrogen and carbon. 

The process is united directly with the electrolytic production 
of the alkali metals. When the vapors of these metals escape from 
the furnace they are conducted, by means of a current of water- 
vapor (?), into an inclosure which is highly heated and where they 
ome in contact with proper amounts of carbon and nitrogen neces- 
sary for their conversion into cyanide. The carbon is supplied in 
the form of carbonic acid, carbon monoxid, hydrocarbon, or even 
finely divided wood charcoal; the nitrogen is supplied in the form 
of ammonia or of atmospheric nitrogen. 

The cyanide formed immediately flows into a receiver for ex- 
ample, a retort communicating with the lower portion of the ap- 
paratus, where it escapes all further reaction. 

It is not indispensable that the alkali metal be produced elec- 
trolytically; it may be produced by any other apparatus and process 

When nitrogen is used, the reaction may be written 

Na + N+C=NaCN+C*_iH a; , tyhuuu(s<ksM tfc ($, 
and when ammonia and carbon monoxid are used the reaction is 

Na + NH 3 + CO = NaNH 2 + H + CO, 
NaNH 2 + H + CO = CNNa + H 2 + H. 

The technics of this process must be most difficult, especially 
in that which relates to the production of the alkali metal vapors, 
and it is difficult to explain satisfactorily how these vapors are 
drawn off with the aid of steam. We doubt therefore if this process 
has been worked, or even set up for work, on an industrial scale. 
Nevertheless, since we knew of its originality we could not omit 
mentioning it, for it shows all the more how far the researches for 
the synthetic production of cyanides has been carried. 

Schneider's Process. This process (German patent No. 9775, June, 
1894; Sept., 1895) has already been much improved. It makes 


use of alloys of alkali metals and the heavy metals, such as lead, 
zinc, or tin, but preferably lead, and these are brought into reac- 
tion at high temperatures with nitrogenous and carbonized mate- 

The advantages in using this method are: A better yield due 
to the greater specific weight of these alloys, their lesser tendency 
to oxidation, and their greater ease of handling than in the case 
of the free alkali metals. The author recommends using an inti- 
mate mixture of the alloy and nitrogenous and carbonized gases, 
stirring with a stirrer, or, better still, by injecting the gases into 
the melted alloy. 

If the gas be brought in contact with the surface of the fusion 
only, the surface of the alloy soon becomes coated with a layer -of 
cyanide, which makes any further conversion into cyanide impossible. 

Here is how the author would proceed, for example, to produce 
sodium cyanide : 

In an iron crucible 80 cm. high and 35 cm. in diameter, an alloy 
of lead sodium containing 10% of this metal is melted beneath 
a layer of sodium cyanide. Into this bath, heated to dull redness, 
is pumped a mixture of acetylene and ammonia in excess. The 
cyanide of sodium formed collects on the surface of the alloy, which 
grows less and less, finally leaving lead almost free from sodium. 

A mixture of monomethylamine and ammonia may be used. 

Castner's Process. The process which, belonging to this type, 
seems the simplest and at the same time the most economical, and 
which appears to give the best results, is that of Hamilton Young 

The process patented by Castner, No. 239644, June 28, 1894, 
is but a repetition of patent No. 239643 of the same date, which 
has already been studied in a previous chapter, but with this differ- 
ence, that the author substitutes ammonia for nitrogen. The reaction 
may therefore be expressed: 

NH 3 + C + Na =CNNa + H 3 . 

The apparatus is the same as that used in the case of nitrogen. 
As the author states, one may also cause dry ammonia-gas to pass 
over heated charcoal, and the resulting gas, consisting of ammo- 
nium cyanide, CN-NH 4 , then passes over fused sodium, where it 


becomes converted into sodium cyanide, with ammonia set free, 
which latter may be recovered and used again in the conversion 
of a fresh quantity of charcoal into ammonium cyanide. In this 
way the reaction is continued with a small amount of ammonia. 
The reactions are: 

NH 4 -CN + Na = CNNa + NH 3 + H. 

Castner has been led to confirm that practically in both these 
methods, either the nitrogen or the ammonia process, intermediary 
reactions are produced, due more or less to the temperature and 
to the proportion of constituents present, which reactions make 
the manufacture rather difficult unless numerous inconvenient pre- 
cautions be taken to avoid loss of metal or of nitrogen. 

These observations led him to - modify his process, which he 
did in the French patent No. 242-938, Nov. 17, 1894. 

In this new process the operation takes place in two successive 
stages, so that the yield obtained is almost theoretical, according 
to the author, and the general character of the method is simpli- 
fied. Moreover, this important modification allows the process to 
be carried on in a continuous way. 

In the first stage of his process, Castner seeks to produce an 
alkali amide by passing anhydrous ammonia-gas over sodium heated 
at a temperature of 300-400, according to the reaction 

In the second stage he converts this amide into cyanide by 
bringing it in a melted state in contact with charcoal: 

-NaNH 2 +C = CNNa + H 2 . 

In practice the process is carried on by means of two retorts. 
In the first retort, specially constructed, the description of which 
will follow, the conversion of the alkali metal into amide takes place, 
and in the second, which is somewhat similar to that used by Castner 
in his first process, the second phase of the process takes place, i.e., 
the conversion of the amide into cyanide. 

One half of the rectangular retort B (Figs. 9, 10, 11) is provided 
with partitions C, which reach low enough to plunge into fused 


metal D. The ends of these partitions are cut short in order to 
allow the gas or vapors to follow the direction indicated by the 

FIG. 9. Castner's Process. Furnace (A) with Rectangular Retort (B} (Elevation). 

arrows. The upper half of the retort is provided with a forked 
entrance tube L, an exit tube M, a bent tube with hopper N pro- 






















FIG. 10. Castner's Process. Perspective of Half of the Retort. 

vided with a valve 0. The lower half is lined with partitions E and 
F, the former reaching a little above the level of the latter, and 
with the partition H reaching a little below partition F. It con- 
tains several openings shown in K. 

The bottom of the retort is provided with an exit tube P, and 
another one R. The rectangular retort is composed of iron. 

The following is the method of procedure in practice: The retort 
B is heated to 390-400, then dry ammonia-gas is conducted into 
it, through the tubes L and U , in order solely to expel the air. 
When this is done, the sodium, which is melted in N, is allowed 


to flow up to the level of the dotted line between E and H. The 
flow of the metal is then for the time being stopped. 

The intake of ammonia is regulated according to the capacity 
of the retort; the sodium flows only at regular intervals, that is, 
for every 17 kg. of ammonia, 23 kg. of sodium are required. 

The amide which forms at the surface of the bath melts and 
sinks to the lower part. It fills the space included between H and F, 
driving the sodium out through the tube R. The overflow of amide 
thus becomes regulated and may be collected in closed vessels, 
being afterward subjected to the further treatment in the process 

FIG. 11. Cross-section of the Retort. 

of forming cyanide, or else it may be transferred directly by appro- 
priate appliances to the retort shown in Fig. 12, where the second 
phase of the process takes place. This second retort is filled with 
wood charcoal and heated to dull redness; the amide flows through 
the tube S, and the hydrogen formed escapes through the tube W, 
while the cyanide produced flows in X. From time to time fresh 
charcoal is added in order to replace that which has been used. 

Castner is one of the few manufacturers who faced the problem 
of the synthetic production of cyanide at a favorable moment. His 
discoveries certainly mark one of the most important advances in 
the history of this interesting industry. His process has been taken 
up in Germany. Important improvements have been added, and 
the day is perhaps not far distant when a real synthetic process 
for the production of cyanide along this line will appear. 

Process of the Deutsche Gold und Silber Scheide Anstalt. Thus 
it is that the above important German firm has just recently taken 
out two patents, one for the preparation of cyanamide, the other 
for the preparation of alkali cyanides, both of which are based on 
the formation of alkali amides, and according to information 
we have been able to gather have given, up to the present time, 


satisfactory results. These two patents present a lively interest, 
and the reader will take it kindly of us if we reproduce them here 
almost entirely. 

The first of these patents (No. 308170) concerns the preparation 
of cyanamide. Up to this time this body had been considered diffi- 
cult of preparation. Frank and Caro, in a process of cyanide manu- 
facture which we have previously described, had already made 

FIG. 12. Castner's Process. Second Phase of the Process. 

known a more practical means of preparing it on an industrial scale. 
The Deutsche Gold und Silber Scheide Anstalt has since that time 
been led to find a process, simple as well as practical, which allows 
its preparation in a really economical way. 

The formula of cyanamide is H 2 N-CN. With metals it yields 
metallic compounds which may correspond to the formula M or 
M 2 -CN-N. Thus, with sodium it yields monosodium cyanamide, 
Na-N-CN, and disodium cyanamide, Na2-N-CN. 


The dialkali cyanamide is prepared by the Deutsche Gold und 
Silber Scheide Anstalt, by starting with the alkali amide obtained, 
as is well known, by the action of ammonia on an alkali metal at 
a temperature higher than the melting-point, but lower than the" 
point of the dissociation of the amide and the ammonia-gas. 

The process is based on this still unknown fact that carbon at 
about 400 displaces hydrogen of the amide and yields cyanamide, 
while at a higher temperature, about 800, it yields, as is known, 

If therefore carbon either in the solid state or in the form of 
hydrocarbon gas be brought in contact, at a temperature of about 
400, with an alkali amide prepared according to well-known methods, 
and in the melted state, cyanamide will be formed. Solid or melted 
amide may also be brought in contact with a solid bath composed 
of a body rich in carbon and heated to a suitable temperature, or 
likewise ammonia at a temperature of 400 may be conducted into 
a mixture of melted alkali metal and charcoal; but in either case, 
the temperature must be successively increased with the corre- 
sponding formation of cyanamide until this temperature be some- 
what higher than the point of fusion of the cyanamide. 

Such is the process for the preparation of the dialkali cyanamide 
as brought out by the Deutsche Gold und Silber Scheide Anstalt. It 
has resulted in obtaining in a practical way the synthseis of cya- 
nides, as we shall presently see. In fact, when treated with charcoal 
at a high temperature the cyanamide becomes converted into cya- 
nide. This method of the preparation of cyanides is an improvement 
over that of Castner, described above, in that the alkali amide used 
by Castner decomposes at a low temperature above 400 while 
cyanamide withstands a temperature up to 800. 

In practice the Deutsche Gold und Silber process is carried out as 
follows : 

In a crucible mounted and built in a furnace which may be well 
and easily regulated, sodium is melted with charcoal or carbona- 
ceous compound (hydrocarbon or other compound) in such quantity 
as will suffice to convert all of the metal into cyanide. When the 
metal has been melted, ammonia is then conducted at a temperature 
somewhat raised (400-600). Under these conditions alkali amide 
is formed which, under the action of a portion of the charcoal, becomes, 


in its turn, converted into cyanamide dialkaline, Na 2 -N-CN. By 
raising the temperature to 700-800 this cyanamide in contact with 
the remainder of the charcoal forms the final product, sodium 
cyanide, NaCN. 

But as the cyanide (a body containing carbon) may also be used 
in the formation of cyanamide, the process may be so arranged that 
a portion of the alkali cyanide found in the crucible at the end of 
the operation may be always left therein in sufficient quantity to 
produce the cyanamide of the next operation, and only sufficient 
charcoal to convert this cyanamide into cyanide need be added. In 
any case a quantity of alkali cyanide corresponding to the alkali 
metal and the ammonia used is always obtained. 

As may easily be seen, this process, which is very ingenious, is 
both practical and economical. Over all the methods thus far 
invented, it has the following advantages, which are to be attentively 
considered : 

1. The operation is carried on at quite low temperatures, which 
prevents, to a considerable extent, loss either of alkali or of cyanide, 
as well as any deterioration of the apparatus. 

2. The process requires only a restricted as well as simple appara- 
tus, since the whole operation may be carried out in one and the 
same crucible. 

3. The yield is quite high, and, according to the authors, is very 
near the theoretical. 

These advantages are certainly to be considered, and there is no 
doubt but that the process of the Deutsche Gold und Silber Scheide 
Anstalt will be applied on a really important scale, thus allowing the 
cyanide to be delivered at a remunerative price. 

We have already called attention to the fact that many investi- 
gators had explained the formation of cyanides, resulting from the 
action of ammonia and carbon monoxid, through the intermediary of 
formamide. We have also seen that the accepted theory is rather 
that of the formation of potassamide. Yet several processes are 
based on the former hypothesis. 

Lambilly's Process. Lambilly, whose name appears at the head 
of most of the innovations of the cyanide industry, is one of the first 
to have based a process for the manufacture of cyanide on this class 
of reaction. 


In his French patent (No. 232697, 1893) Lambilly carried on his 
new method as follows: 

Into one or several tubes heated to a temperature between 40 
and 150 and filled with porous substances, a mixture of carbon 
monoxid and ammonia is conducted, according to the reaction 

NH 3 +CO = H.CO-NH 2 . 


This formamide, when heated at a temperature above 210 in a 
second group of tubes filled, as in first case, with porous substances, 
is decomposed with formation of hydrocyanic acid: 

. ^ ( 


Martin's Process. This process (French patent No. 262949, Jan. 
11, 1897) consists in bringing atmospheric nitrogen into reaction with 
methane in definite quantities (the amounts are not indicated by 
the author) contained in a retort constructed of refractory brick 
which is charged with porous substances which have previously 
been metallized with platinum, titanium, vanadium, or magnesium. 
Under these conditions the methane breaks up into acetylene and 

Under the influence of heat, nitrogen, and hydrogen, the acetylene 
in the nascent state is decomposed into gaseous cyanogen products, 
which are conducted into a cylinder adjoining the retort and con- 
taining fragments of potassa-lime heated to redness. In this way 
potassium cyanide is obtained, which may be separated by filtration 
and crystallization. We are not in possession of any further data 
concerning this process, nor of its working. 

Clock's Process. This process (German patent No. 108152, March 
15, 1899) still utilizes the property which formamide has of breaking 
up into water and hydrocyanic acid. 

Clock heats, in an autoclave at 200-300, ammonium formate 
alone, or mixed with ammoniacal zinc chloride, yielding formamide 
which distils 

HC0 2 NH 4 = H 2 + H . CO - NH 2 , 

its vapors being conducted over melted potassa or soda, or a mixture 
of the two, heated to 250-350. If the formamide still contains 


moisture and unconverted ammonium formate, the alkali should be 
heated above 360. The reaction consists in dehydrating the forma- 
mide under the influence of the melted alkali, a dehydration which 
gives rise to hydrocyanic acid which becomes fixed immediately by 
the alkali with formation of cyanide. 

Two other processes which are quite peculiar and original and 
which are based on quite different principles from those already 
studied will be mentioned. 

Huntington's Process. The first is that of Kirby Huntington 
(English patent No. 14855, Aug. 6, 1895; German patent, No. 16931, 
Jan. 1896, April, 1897; French patent No. 253740, Feb. 5, 1896). 

In this method the inventor produces hydrocyanic acid by means 
of rapid deflagration of a mixture of equal volumes, or of 105 vols. 
nitric oxid and 100 vols. acetylene in a cylinder with firm walls: 

C 2 H 2 + NO = CNH + CO + H. 

The mixture of the two gases serves as a motive force for an 
ordinary gas-motor by the use of the electric spark. 

The gases which issue from the cylinder pass through a series of 
absorption apparatus filled with strong alkali solutions. The hydro- 
cyanic acid is absorbed and forms cyanides, whereas the hydrogen 
and the carbon monoxid are collected in a gasometer and may be 
used as fuel. 

This process does not appear to us to have given satisfactory 
enough results to warrant its use industrially. 

Hoyermann's Process. The second of these processes is that of 
Hoyermann (French patent No. 294979, Dec. 5, 1899). It is but a 
modification of Huntington's process, in which it is sought to avoid 
the formation of carbon monoxid and hydrogen which takes place 
in that process. Instead of using nitric oxid, Hoyermann employs 
nitrogen, according to the reaction already indicated by Berthelot, 

C 2 H 2 +2N=2CNH. 

The reaction takes place in a carbide electric furnace. The 
electrodes are hollow and are used for the introduction of the acety- 
lene and the nitrogen which they bring separately into the zone of 
action of the luminous arc. The mixture and the union of the two 


gases take place at that point. Calcium carbide may likewise be 
produced in the furnace, and on the addition of water-vapor, acetylene 
may be formed. At the same time, the introduction of air, which 
comes into contact with the acetylene, yields hydrocyanic acid under 
the action of the electric arc. The hydrocyanic acid thus formed is 
removed by means of a suction-pump, collected and absorbed by 
suitable means. 

Moreover, the process may be made continuous. In fact, under 
the action of water-vapor, calcium carbide becomes decomposed 
into acetylene and lime, which latter, on careful addition of pieces 
of charcoal, may be intermittently transformed anew into carbide. 

This process does not seem to us to be any better suited to indus- 
trial purposes than the preceding one. 

Nitric and nitrous nitrogen have also been employed. 

Roussin's Process. Roussin has noted that if a mixture of 
fused potassium acetate, potassium nitrate, and potassium carbo- 
nate be dissolved in a small amount of water .and evaporated to dry- 
ness and the residue be fused, it deflagrates violently at 350, leav- 
ing behind a black spongy mass containing a large quantity of 
cyanide of potassium mixed with potassium carbonate and char- 
coal. But this method has one disadvantage in that 3 /4 of the 
carbon of the acetate is converted into carbonic acid by the oxygen 
of the nitrate. To overcome this disadvantage Roussin proposes 
the use of potassium nitrite mixed with lampblack, acetate, and 
carbonate of potash. 

Kerp's Process. Wilhelm Kerp (Ber. d. d. Chem. Gesell. 1897, 
p. 610) observed that when sodium acetate is fused with potassium 
nitrite, there is formed potassium cyanide according to the reaction 

CH 3 CO ONa + KN0 2 = C0 3 HNa + CNK + H 2 0. 

The yield of cyanide depends to a large extent on the tempera- 
ture; in no case does it exceed 25%, and the reaction often yields 
considerable quantities of hydrocyanic acid. According to the 
inventor, the reaction should take place thus: In the first phase 
of the reaction there is formed caustic soda and nitroacetate of 

NaOH+NO-CH 2 -CO-ONa. 


This salt is then broken up into bicarbonate of soda and 
hydrocyanic acid: 

NO -CH 2 -CO -ONa= C0 3 NaH+CNH. 

A portion of the hydrocyanic acid thus formed combines with 
the caustic soda, the rest escaping. This is therefore a process 
which is not applicable to industrial purposes. 

Kellner's Process. This process (French patent No. 252282, Dec. 
9, 1895) consists in subjecting to the electric arc an alkali nitrite or 
nitrate with or without addition of charcoal to facilitate the 

Siepermann had previously tried to utilize the same reaction, 
but in a reverberatory furnace. With this object in view, he injected 
pulverized alkali nitrite or nitrate into a reverberatory furnace by 
means of compressed air, the furnace being charged with charcoal 
alone or charcoal to which had been added a small amount of car- 
bonate. The cyanide formed flowed through a draft-hole situated 
in the most sloping place of the sole. As a portion of the cyanide 
formed became volatilized at the high temperature at which it was 
necessary to carry on the reaction, the gases escaping the furnace 
passed through condensation chambers or absorption towers, where 
they gave up this salt. 

Grossmann's Process. Jacob Grossmann's process (1900) is a 
rather curious one. It is based on the reaction, already known, 
that if liver of sulphur be melted in the presence of charcoal, and 
then ammonium sulphate be added to the fused mass, a very lively 
reaction (sometimes even an explosion) takes place which yields 
sulphocyanide of potassium. This process, studied by Fleck in 
1863, had not been tried on an industrial scale. Grossmann took 
up the process anew, and modifying the nature of the reactions, 
made out of it a method for the direct manufacture of cyanides. 
He noted that if ammonia be passed over a mixture of liver of sul- 
phur and charcoal heated to redness (700-800), potassium cyanide 
is formed; sulphocyanide is formed only in a secondary way, the 
greater portion of the sulphur being converted into either hydrogen 
sulphide or ammonium sulphide. 

If the sulphide already formed be used, the process requires 


equal parts of sulphide and of wood charcoal; when liver of sul- 
phur is used the following proportions are necessary: 

Carbonate of potash (pure) 100 parts 

Charcoal 120-140 " 

Sulphur 24 " 

These quantities are necessary to prevent heaping together. 

Under this heading will be mentioned processes which have 
been proposed for the production of cyanides, and which do not 
belong to any of the preceding classes According to information 
obtained by us, it follows that, with the exception of Dr. Bueb's 
process, the other processes have either not been tried at all or to 
a very limited degree ; yet we shall mention them in order to show 
the variety of ideas brought out concerning the manufacture of 
cyanides, all of which indicate the interest and importance of this 

Process of the Chemische Fabrik Aktiengesellschaft. One of the 
most interesting processes of this class is that of the Chemische 
Fabrik Aktiengesellschaft of Hamburg (German patent No. 5242, 
1894-1895, and French patent No. 241146, 1894-1895). 

It consists in heating to redness sodium or potassium carbazol 
with or without the addition of sodium or potassium hydrate or 
carbonate, and in case it is desired to produce ferrocyanides, with 
the addition of iron. 

Carbazol is obtained in the residues from the purification of 
crude anthracene (by means of benzene, sulphurous acid, etc.), 
which residues contain large amounts of it. These residues are 
treated with dry or slightly moist caustic alkali corresponding to 
the amount of carbazol present. This treatment takes place in a 
cast-iron pot provided with a stirrer. Heat is applied gradually 
till the temperature reaches 260-280 when potassa is used, and 
to 320-340 with soda. This temperature is maintained for several 
hours. The alkali carbazol formed separates out clearly from the 
other compounds 'hydrocarbons, etc.). It is collected separately 
and to it is added an excess of caustic soda or potash or their car- 
bonates, and i on, if the object be to prepare ferrocyanides. The 
mixture is then heated to bright redness. The fused mass is taken 


up with water and treated according to any of the ordinary methods 
for the separation of cyanide or ferrocyanide. 

In practice the method of procedure is as follows: 200 kilos of 
residue from the purification of anthracene, containing 40% or 
thereabouts of carbazol, are treated with 30 kilos caustic potash. 
The heat is kept at 260-280 until all the water separated by the 
union of the carbazol with the potassa has distilled, which requires 
about three hours. The stirrer is then stopped, and after a quarter 
of an hour's repose, the product is run into moulds. The whole 
solidifies; but after cooling, it is easy to separate the solid cake 
of potassium carbazol which lies at the bottom of the moulds from 
the more or less soft crystalline magma formed with floating anthra- 
cene carbides. The crude potassium carbazol is crushed and again 
heated in an apparatus similar to the one mentioned above, capa- 
ble of being heated to bright redness. The temperature is gradu- 
ally raised to this point, and under these conditions the potassium 
carbazol becomes converted into cyanide with separation of car- 
bon and liberation of some ammonia and combustible gases. A 
greater yield may be obtained by carrying on the fusion in the pres- 
ence of an alkali used as a flux. Unfortunately we have no data 
concerning the yield produced by this process. 

VidaPs Process. This process (German patent No. 2868, 1897; 
French patent No. 274875, Feb. 9, 1895) uses phospham. 

If a mixture of 6 kilos of phospham and 19 kilos potassium car- 
bonate be heated to redness up to complete desiccation of the phos- 
phorus, there will be formed potassium cyanate and phosphate 
according to the reaction 

PN 2 H + 2C0 3 K 2 = PO,K 2 H + 2CNOK. 

The mass may be treated with water or alcohol, which dissolves 
the cyanate, leaving the less soluble phosphate behind. 

But if to the charge used above charcoal be added in the fol- 
lowing amounts, 

Phospham 6 kilos 

Potassium carbonate.. 19 " 

Charcoal 1J ". 


cyanide of potassium will be obtained: 

PN 2 H + 2C0 3 K 2 + 2C = 2CNK + 2CO + P0 4 K 2 H. 

By adding 0.8 kilo of iron or 4 kilos of sulphur to the above 
charge ferrocyanide or sulphocyanide will be obtained. 

The carbonate may be replaced by neutral or acid oxalate which 
yields cyanogen or hydrocyanic acid, which escapes, or the phospham 
may be heated to 150-200 with fatty acids. Thus, with formic, 
acid, there is formed hydrocyanic acid: 

PN 2 H+2C0 2 H 2 =P0 4 H 3 +2CNH. 

The operation is carried on as follows : 60 kilos phospham are placed 
in an enamelled cast-iron pot and heated in an oil-bath to 150-200. 
Then 48 kilos formic acid or 63 kilos acetic acid are rapidly run in. 
Hydrocyanic acid is collected by the usual means. 

We do not know whether this process has been tried. 

To conclude this last part, we shall take up certain processes 
whose object is to extract in the form of cyanide the nitrogen con- 
tained in the residues of the refinery and of the distillery. The 
molasses and vinasse contain, as is well known, variable amounts 
of nitrogen (0.5-2.5%). Various methods have been proposed for 
regaining this nitrogen in the form of ammoniacal liquors or of 
ammonium sulphate, but most of these methods have not continued 
in use for any length of time. The product obtained is largely 
contaminated with amines formed during ignition, which are diffi- 
cult to separate from the ammonia. Among them are trimethyl- 
amine dimethylamine, monomethylamine, monobutylamine, and 
monopropylamine. Moreover, the gases which escape during the dis- 
tillation of the molasses and vinasses spread abroad in the surround- 
ing atmosphere an odor which is tainted and injurious to the public 
health. Besides avoiding this disagreeable odor, Bueb's processes 
furnish cyanide cheaply and in a relatively simple manner. 

Bueb's Processes. In his first French patent (No. 246282, April 
1, 1895) Dr. Julius Bueb conducts* the gases which escape during the 
distillation of the vinasses and molasses into a system of vessels 
or refractory tubes heated to bright redness or to a white 


In this way all the volatile compounds of nitrogen which they 
contain are entirely converted into ammonium cyanide mixed with 
a, little ammonium carbonate. On emerging from the system of 
tubes, the gases pass into suitable solutions (ferric salts). 

The vinasses at 40 B. are introduced into the furnace A (Figs. 
13, 14, 15, 16). Toward this end they are made to flow from the 
upper reservoir a into the receptacle &, and by means of a siphon 
c into the retort, where a liberation of gas immediately begins. The 
gases of the distillation are collected in the tube e and transmitted 

FIG. 13. Bueb's Process. 

directly into the pipes /. These pipes go through the furnace in 
zigzags, and are so arranged that the gases require about 15 seconds 
in passing through. 

After passing through these pipes, the gases are conducted to 
the absorption apparatus. The heating of the furnace may be done 
by means of the gases from the distillation after first freezing them 
from the cyanogen compounds. They first heat the pipes / by 
passing under them by way of the passage k; then above, through 
the space ki ; . and lastly they likewise heat the retort by way of the 
passage k 2 . The temperature of the pipes is between 1000 and 
1100, that of the retorts 700-800. 



By means of this process, Bueb obtains a gaseous mixture com- 
posed to a large extent of hydrocyanic and carbonic acids. In 
order to separate these two gases, he uses the same method that 

FIG. 14. Bueb's Apparatus. 

is used in extracting cyanogen from coal-gas ; that is, its absorption 
by means of iron salts, the result of which being the formation of 

FIG. 15. Bueb's Apparatus. 

a double ferrocyanide which may then be converted at will into 
alkali cyanide. 

Later, Bueb was led to separate hydrocyanic acid from car- 



bonic acid directly in the form of alkali cyanide. To this end he 
proceeds as follows (French patent No. 283968, Dec. 13, 1898). 

The gaseous mixture is first cooled down, and in case it con- 
tains ammonia, it is made to pass into dilute sulphuric acid (20%). 

Thence it is conducted to a tower through which a stream of 
very strong alcohol flows in the opposite direction. The alcohol 
dissolves only the hydrocyanic acid, so that a solution of hydro- 
cyanic acid flows at the bottom of the tower. This solution is 
subjected to a fractional distillation, and the vapors of hydrocyanic 
acid are then combined in the usual way. 

For this purpose it is possible, and it is moreover the method 
which the author particularly recommends, to have the vapors of 
acohol and hydrocyanic acid pass through an alcoholic caustic 
alkali solution. Alkali cyanide, which is formed, being quite diffi- 
cultly soluble in alcohol, is precipitated in the form of a white powder. 
The alcohol is condensed and used again in repeating the operation. 

After absorption, the vessels containing the lye, when cooled, 
are connected with an aspirator. After the aspiration, there remains 
in the apparatus practically pure alkali cyanide (98%). The mother 
liquors which flow from the aspirator, and which contain 2 to 4% 
alkali cyanide, are conducted into a saturation apparatus placed 
in front of the tower through which alcohol flows, and the gases 
passing through precipitate the alkali as carbonate, while the alcohol 
becomes saturated with the hydrocyanic acid which is converted 
into cyanide as before. 

In his patent No. 296793, taken out in 1900, Bueb states that 
during the dry distillation of vinasses the gases which pass through 
the narrow tubes where the conversion into cyanide takes place 
deposit, when heated, particles of carbon which obstruct these 
pipes and hinder, to a considerable extent, the regulation of heat. 
In order to remedy this inconvenience, he proposes the following 
arrangement : 

The distillation takes place in retorts filled with pieces of refrac- 
tory substances previously heated to the required temperature. 
When this temperature has been reached, the heating is discon- 
tinued, and the gases are passed through. These gases become 
rapidly heated through the heat of these refractory contact-bodies 
and are converted into cyanide compounds. During this opera-* 


tion, the gases deposit upon these contact-bodies charcoal to such 
an extent that they become coated therewith. When this point 
has been reached, the supply of gases to this oven is stopped, and 
instead they are conducted to another oven already heated during 
this first stage of the process. During the second stage the appa- 
ratus, which has been exhausted, is heated anew, and at the same 
time the calorific power of the deposited carbon is utilized in heat- 
ing the refractory contact-bodies for the next operation. Thus, the 
process may be carried on continuously, and besides, the deposited 
charcoal, which used to be a serious danger in the cyaniding process, 
is utilized. 

Bueb's processes are used on an industrial scale to a consider- 
able extent in Germany, where quite favorable results are obtained 
they are regularly in operation in one of the largest sugar- works. 
The raw salts of vinasses obtained appear to be better. In any case, 
the process may be easily adapted to refineries and distilleries with- 
out modifying in the least their usual course, and it would allow 
considerable extra revenue to be derived from the beet residues. 

The idea is, moreover, not entirely new, for from 1894 the Societe 
anonyme de Croix (Nord) manufactured cyanides from trimethyl- 
amine. As is known, this compound, corresponding to the formula 
N(CH 3 ) 3 , is obtained in large quantities in the dry distillation of 
beet residues. It is formed by the decomposition of the two alka- 
loids found in beet-juice, betaine and cholin. The ordinary molasses 
may contain as much as 5-13% betaine. From Bressler's investi- 
gations, it follows that in 100 parts of nitrogen of beet residues, 
20.67 parts belong to betaine and 20.32 to cholin; and in 100 parts 
nitrogen in the products of distillation of the beet residues, 26.76 
parts are in the form of trimethylamine. Moreover, most of the 
alkaloids, on decomposing, yield trimethylamine, and the distilla- 
tion of wood also gives a certain amount of it. 

Ortlieb and Muller's Process. The process of the Societe anonyme 
de Croix is due to Ortlieb and Muller, and is based on an old reac- 
tion pointed out by Wurtz (Ann. de Chim. et Phys. XXX, p. 454), 
which is as follows: If trimethylamine be passed through a porce- 
lain tube heated to redness, there is formed hydrocyanic acid and 
ammonium cyanide. 

Ortlieb and Muller's process is simply the application of the 


above reaction. Commercial trimethylamine is first vaporized in 
specially constructed boilers. These vapors are then conducted 
into retorts similar to those used in gas manufacture, and heated 
to redness, when they are broken up into hydrocyanic acid and 
ammonium cyanide. The products of this de omposition are con- 
ducted through a series of absorption apparatus. The first series 
contains dilute sulphuric acid. The ammonium cyanide is there 
decomposed into sulphate of ammonia, which remains in solution, 
and hydrocyanic acid, which together with that already formed 
in the gaseous mixture, passes on into the other absorbers. These 
contain either sodium or potassium hydrate, or milk of lime, or any 
other alkaline-earth hydrate. 

The alkaline solutions absorb the hydrocyanic acid, yielding 
concentrated solutions of the corresponding cyanides, while the 
residual combustible gases, completely freed from prussic acid and 
ammonia, are collected in a gasometer and used as a source of 
illumination. This process allows the recovery, in the form of 
ammonium sulphate and cyanide, of the whole of the nitrogen of 


FERROCYANIDE of potash, or yellow prussiate of potash, has long 
been, together with Prussian blue, the only cyanide compound 
known and manufactured. It served a long time as the basis for 
the manufacture of cyanides, and at the present time 50% of the 
ferrocyanide produced is still used for that purpose by means 
of the processes which were reviewed at the beginning of Part I. 

Ferrocyanide may be produced in an industrial way by two 
distinct classes of processes: 

(1) Those based on the use of nitrogenous organic substances. 

(2) Those which utilize the spent oxides from the purification 
of illuminating-gas, or those whose object is to extract the cyanide 
compounds directly from this gas. 

Other processes have been likewise proposed. But most of 
them produce cyanides as intermediary compounds, and they have 
been studied in the previous chapter. It should also be mentioned 
that all the synthetic processes proposed for the production of 
cyanides may likewise be employed in the manufacture of ferro- 
cyanides, either by adding metallic iron to the cyaniding substances 
or by treating the cyanided masses with strong solutions of ferrous 

The present chapter will consist of two parts: 

(1) Manufacture of ferrocyanides by means of nitrogenous sub- 

(2) Manufacture of ferrocyanides by means of illuminating-gas 
or of the masses which have served in its purification. 




These processes were for a long time the only ones employed in 
the manufacture of potassium ferrocyanide. At the present time 
they have almost wholly been abandoned, there being but a few 
works (in Germany, England, and the United States) still in oper- 
ation. However, as many important studies and investigations 
have been conducted along the line of these processes, and, more- 
over, as the industry of the cyanide compounds is derived from 
them, we shall describe them more or less at length. 

They consist, practically, in igniting nitrogenous organic sub- 
stances in the presence of potassium carbonate and charcoal. Under 
these conditions (without entering at present into the discussion of 
the reactions which take place in this formation) there is formed 
potassium ferrocyanide through the union of the four elements iron 
nitrogen, carbon, and potassium: 

Fe(CN) 6 K 4 . 

The discovery of ferrocyanide proceeds from that of Prussian 
blue; but it came about much later. It is known that Prussian 
blue, discovered by Dippel, was prepared by the ignition of dried beef- 
blood in the presence of potassium carbonate, the mass thus obtained, 
on treatment with water, giving a solution known as "blood-lye," 
which when treated with an iron salt yielded Prussian blue. For 
a long time the composition of "blood-lyes" was unknown. 

In 1752, Macquer succeeded in regenerating this product by 
treating Prussian blue with an alkali, and his ideas concerning the 
nature of this reaction led him to give it the name of phlogisticated 

Toward 1780, Sage, and later Bergmann, successively established 
that these "blood-lyes" yielded on concentration and crystallization 
a definite body, to which they gave the name of "blood-lye" salt, 
a name which it held for a long time. 

It was not until 1823, thanks to the remarkable researches 
of Gay-Lussac, that the composition of this salt was known, which 
is ferrocyanide or cyanoferride of potassium, more commonly called 


yellow prussiate of potash. Such was the beginning of its manu- 

As a rule, all nitrogenous organic substances, whether of vegetable 
or of animal origin, may be utilized for the preparation of ferro- 
cyanide. But, as has already been remarked, these substances 
almost always possess a considerable value because they may be 
employed either in feeding or in domestic economy. They are 
too expensive. Therefore the yellow prussiate industry makes 
use of the residues or waste products the value of which is much 

We have seen that at first dried beef -blood was used. In 1724 
Brown proposed to substitute for it meat, and finall in 1725, Geffroy 
made use of wool wastes and hartshorns. 

The organic substances used in the maunfacture of yellow prus- 
siate may be divided into five classes: hair, rags, horn, leather, and 

Under the term horn are included hoofs, the claws of animals, 
points of horns, defective horns, the wastes from the manufacture of 
combs, buttons, etc. 

Hair and rags, which are often put in the same class, include 
bristles of swine and hair unfit, for the manufacture of the various 
kinds of brushes, wool wastes, the hair of domestic animals, the 
wastes of woolen cloth which cannot be used in paper-making, 
damaged cloth, and the trash obtained in trimming cloth, generally 
called shearings. 

Leather may be divided into two groups: 

(1) The wastes or clippings of new leather, i.e., the wastes of 
harness-shops, morocco-leather manufactories, shoe-shops, tanneries. 

(2) Old leather, more commonly called old shoes. 

Red leather is to be preferred, chamois leather is rarely used, 
and white leather never. The wastes of kid-glove manufactories 
cannot be used on account of the presence of alum. 

By tendons it is understood the slaughter-house detritus, certain 
portions of dead animals, and the dried muscles of these same animals. 

The composition of these different products depends upon the 
circumstances inherent in the treatment to which they have been 
subjected, or upon the condition in which they have been found. 

Three essential elements must be taken into consideration in 


the substances used for the manufacture of ferrocyanide, viz., the 
percentage of nitrogen, of sulphur, and the amount of ash. 

Upon the richness in nitrogen depends the value of these sub- 
stances and therefore the yield in prussiate. This is therefore of 
first importance. As to the other two elements, they are interesting 
only so far as they exert a detrimental action on the yield. 

In fact, in proportion as these two elements are present is the 
percentage of nitrogen less. Moreover, the sulphur may unite and 
form sulphocyanide, which reduces by so much the yield of ferro- 
cyanide. This objection may be avoided by adding iron to the 
mass; the iron sulphide formed will be converted into ferrocyanide 
when the mass is lixiviated. The composition of the ash should be 
taken into consideration; phosphoric acid and silica exert a detri- 
mental action on the formation and crystallization of ferrocyanide. 

The following table gives the composition of the nitrogenous 
organic substances most generally used in the manufacture of ferro- 

It should be mentioned, as will be seen on examining the table, 
that the organic substances contain three times as much, and some- 
times more, carbon as nitrogen, while yellow prussiate contains 
these two elements in about equal proportions (116 of carbon, 120 
of nitrogen). 

The nitrogenous organic substances, when subjected to ignition^ 
lose i of their nitrogen in the form of ammonia or ammoniacal com- 
pounds at a temperature below that of the formation of cyanide. 

Thus, these substances are often subjected to a previous ignition 
at a low heat, during which the ammoniacal products set free are 
collected. The residue is animal charcoal, containing the rest of the 
nitrogen. The percentage of nitrogen itself varies, depending upon 
the process of ignition, the percentage decreasing with the increase of 
temperature of ignition. In general one seeks to produce a charcoal 
containing 4-5% nitrogen, which corresponds to about a f diminution 
of the mass. 

This ignition takes place in cast-iron boilers 1 meter high and 1 
meter in diameter the cover of which is provided with .an exit tube 
connected with an apparatus which serves for the absorption of the 
ammoniacal compounds. Since the bottom wears away so rapidly 
it is so arranged that it may easily be replaced. 





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The second raw material in the manufacture of yellow prussiate is 
potash. Generally commercial potassium carbonate is used, which 
often contains other salts such as sulphate, silicate, chloride of 
potassium, and sometimes sodium salts. The chlorides exert no 
influence; the sulphates form sulphides during the process, which 
attack the cast metal and rapidly puts the apparatus out of service. 
The silicates and earthy substances likewise exert an injurious action. 

One may likewise use blue potash extracted from the mother- 
liquors of a previous manufacture, a product which contains 40-90% 
potash, but 4-8% potassium sulphide, 7-16% potassium silicate, 
7-13% potassium chloride. It is therefore necessary to subject 
these substances occasionally to purification, for their coefficient of 
impurities increases with the successive number of ignitions. 

The iron, which is often added to the ignition, may be used in 
the metallic form (nails, filings, wastes from tin-plate), or oxid 
(forge scales), which becomes reduced at the beginning of the igni- 
tion. The forge scales are often objectionable because they contain 
a large amount of combined silica, and earthy matters. 

The manufacture of potassium ferrocyanide Comprises three 
distinct stages: 

1. Ignition or production of the metal. 

2. Lixiviation of the metal. 

3. Crystallization. 

i. Ignition or Production of the Metal. By the name metal 
is meant the crude product resulting from the ignition of the nitrog- 
enous organic substances in the presence of iron and alkali. 

The amount of these raw materials to be used is as follows: 

Carbonate of alkali. . 100 parts 

Nitrogenous substances (130-140 at a maximum, 170 

with animal black) 125 "' 

Metallic iron r 6 or 7 " 

The whole mixture of these substances may be charged in retorts 
or ovens, but it is much better first to add the potash, then to shovel 
in the animal substances. 

In fact, under the influence of the high temperature necessary 
to carry on the reaction, an abundant liberation of combustible 
gases is produced (carbon monoxid, carbides, carbonic acid), which 


remove from the mass a large amount of heat. The successive 
additions of animal substances to the mass restore to it the amount 
of heat lost. To carry on the reaction in the best way, it is necessary 
that the temperature be always sufficiently high that the alkali 
carbonate may be reduced by the charcoal, but it should not be 
too high, otherwise some of the cyanide formed will be volatilized. 

The operation takes place in iron kettles, or in specially con- 
structed retorts, or in reverberatory furnaces. 

The oldest apparatus known is pear-shape (Fig. 17). This 
oval or pear-shaped retort (A) is of iron and rests on one side, on 

FIG. 17. Pear-shaped Retort for the Manufacture of Ferrocyanide. 

A, retort; D, fire-grate; C, vault; E, flue for the outlet of gases; B, opening 
for charging and unloading; G, kettle for the evaporation of the strong solutions. 

the stonework of the oven, by means of a powerful trunnion, and 
on the other, on the facade wall of the oven by its neck. It thus 
presents a slight inclination backward. It is 1.20 meters long, 
0.80 meter in diameter, and 0.15 meter thick. The rounded 
part of the retort is free, and is completely exposed to the action 
of the flame which arises from the grate D. The opening B, which 



serves to load and unload the retort, is closed by a sheet-iron lid. 
The products of combustion, coming from the fire-grate D, are 
distributed on each side of the retort, and again come together 
in the arch C and escape by means of the flues E. The heat lost 
from these gases is utilized in evaporating the strong solutions in 
the vessel G. The retort A may be turned over from time to time 
in order to change the surface coming in direct contact with the 
flame and to avoid a too rapid wear and tear. There are two objec- 

FIG. 18. Reverberatory Furnace. 

tions to this class of apparatus: they wear out very rapidly, and 
the action of the heat may be exerted on the substances only through 
the walls of the retort. 

The pear-shaped retort has been replaced by the reverberatory 
furnace. The sole of this furnace consists of a cast-iron cupel (7 
(Fig. 18) 1.1 meters in diameter and 0.10 meter thick. The fuel is 
put on the grate B, the products of combustion follow the conduit E 
in the direction indicated by the arrow, and come to the vault A, 
where they heat the cyaniding mixture from above, and in this 
way the high temperature necessary for the reaction is more easily 


In some works the gases of the grate pass under the cupel 
before coming in contact with the surface of the mixture. On com- 
ing out of the vault A the gases .pass through a lateral tube and 
thence through the chimney F, whence they are conducted under 
evaporating-kettles which they heat. 

In these furnaces 500 kg. of material may be converted at one 
time into yellow prussiate. The cupels wear out rapidly, but 
can easily be replaced; thus, after 700 tappings, a 1500 kg. cupel 
will weigh no more than 250 kg., and should not be used fur- 
ther. The wear and tear is particulary rapid in the case of fur- 
naces with double circulation, where the combustion gases pass 
above and below the cupel. These furnaces have been used quite 
extensively in Germany. 

The operation is as follows: The cupel is first heated to red- 
ness. When this is done, the inlet of gases is shut off and the mix- 
ture of potassium carbonate and blue potash is introduced into 
the cupel, and the cover closed. The gases are let on again and 
the mass brought to fusion. When this is in perfect fusion, the 
poker is introduced and the nitrogenous substances shovelled 
in, mixing them in the mass with the aid of the fire-iron. A lively 
reaction takes place, accompanied by effervescence and an abun- 
dant liberation of combustible gases which burn at the surface of 
the bath with flames sometimes, 2 meters in length. 

To prevent the fused mass from overflowing, small portions of 
nitrogenous substances are added whenever the reaction- becomes 
too lively. When about half 'of the nitrogenous substances has 
been added, the reaction becomes more gentle; further addition is 
stopped for V2- 8 /4 of an hour, during which time the mass is vigor- 
ously stirred with the poker until the bath is completely fluid. The 
rest of the organic substance is then added in 2 or 3 portions. All 
these operations require about 2 hours. The mass is again heated 
for l / 2 hour, after which it has the appearance of a thick liquid, 
and is run into moulds with the help of an iron spoon. After cool- 
ing, it has the appearance of loaves of bread. As a rule, 6 tappings 
of 250 kg. each may be made for each furnace every 24 hours; but, 
of course, the length of the operation varies according to the nature 
of the substances acted upon, the intensity of the fire, the experi- 


ence of the workman using the poker, etc. In any case it varies 
from 4 to 6 hours. 

In England, preference was given to vertical cast-iron boilers, 
slightly narrowed at the opening and provided with a mechanical 
stirrer whose axle penetrated the cover, and set in motion by means 
of gears connected with the source of power. This arrangement 
allowed a good deal of manual labor to be spared. Generally these 
boilers were arranged in series of 24. 

Although this method has certain advantages, it has great dis- 
advantages. The greatest objection consists in the losses, which 
are appreciable, due to the fact that the nitrogenous substances 
float on the surface of the bath and there burn, the nitrogenous 
gases liberated thereby coming in contact with but a thin layer 
of potash and thus escape without being combined. 

Engler's process has the object in view of obviating this diffi- 
culty by causing the nitrogenous gases to become liberated in 
the very midst of the mass itself. 

Engler's Apparatus. This consists of a vertical boiler 60 centi- 
meters in diameter and 2 meters high. A piston, formed by a per- 
forated sheet-iron disc and moved to and fro, continually rams the 
nitrogenous substances into the very mass itself. First, 300 kilo- 
grams of potassium carbonate are placed in the boiler; when this 
is melted small portions at a time of nitrogenous substances are 
added through the hopper (the piston being lowered), till the 
whole of the nitrogenous substances has been added. The unload- 
ing is done from beneath, and the mass is collected in a suitable 
truck. The ammonia set free during the reaction is collected in 
a tower filled with pieces of coke. 

The product of ignition obtained in either one of the processes 
just described is a greenish-black mass, quite hard, porous, absorb- 
ing atmospheric moisture energetically, with liberation of ammonia 
and hydrocyanic acid. This is the mass which is commonly called 
metal. It yields about 16% potassium ferrocyanide. Its compo- 
sition varies, of course, with the composition of the substances used, 
the length of the operation, and the method used in carrying it on. 

Karmrodt, who took the average of ten tappings, produced by 
igniting 100 parts of potash, 100 parts nitrogenous material, and 
10 of iron, gives the following figures: 


Cyanide of potash 8 . 20 

Sulphocyanide of potassium 3 . 33 

Cyanate of potassium 2 . 46 

Carbonates of sodium and potassium 57. 56 

Sulphate of potassium 2 . 82 

Silica 3.10 

Insoluble. . . * 18. 11 

Undetermined. . 4.42 


As may be seen, the metal does not contain any ferrocyanide. 
This salt is formed only on lixiviation. 

The metal is broken into lumps as large as one's fist and thrown 
into vats containing water or weak solutions from a previous opera- 
tion; this is heated to 60-90 for 12 to 14 hours while stirring. 
The temperature should not exceed 90, nor be kept at that point 
too long, for the cyanide might be converted into ammonia and 
potassium formate. 

When all the solid pieces have disappeared and the solution 
-shows about 24 B., it is allowed to stand 3 or 4 hours, after which 
the clear liquid is decanted. The residue is washed with fresh 
water, the washings being used in lixiviating the succeeding metal. 

The clear liquid or " blood-lye," which is greenish black in color, 
is concentrated in kettles by the waste heat from the ignition furnaces 
until the solution shows 32 B. It is finally run into wooden crys- 
tallizing vats, where it deposits on cooling a grayish crystalline 
product, called crude salt, containing about 1 / 6 of its weight of fer- 
rocyanide of potassium. 

This crude salt is withdrawn and placed in wicker-baskets in 
order to drip. It is purified by a second and sometimes a third 
* crystallization. The final product is a lemon-colored salt potassium 
lerrocyanide, Fe(CN 6 K 4 +3H 2 0. 

When th mother-liquors are concentrated to 40 B. a fresh 
quantity f very small crystals appears, which are purified by 
repeated crystallization. 

Gentele avoids the second crystallization by precipitating the 
ferrocyanide completely from its solution at the boiling-point. The 
lyes at 35 B. are heated to boiling. Under these conditions the 


salt is deposited; this is withdrawn and allowed to drip. When the 
lyes show 50 B., the boiling is stopped and the lyes allowed to 
stand overnight, when the rest of the cyanide is deposited. In 
this way no very small or "fat" crystals are obtained; the mother- 
liquors are treated directly in order to obtain the blue potash. Gen- 
tele's method of obtaining the crude salt yields somewhat more 
potassium sulphate than the ordinary method. 

It remains but to purify the crude salt obtained by either of 
these two methods; to this end, it is dissolved in just enough hot 
water so that the solution shows 32 B. It is allowed to stand and 
is then drawn off or filtered in order to separate the black par- 
ticles of insoluble residue which detract from the appearance of 
the product. The clear solution is then transferred to rather deep 
wooden or sheet-iron crystallizing vats which are surrounded by 
insulating bodies, where it is left during 8-10 days. The ferro- 
cyanide is deposited, the mother-liquors being drawn off carefully 
and used to dissolve a fresh amount of crude salt, while the crys- 
tals are covered over with a new solution sufficiently concentrated 
to add to the crystals already deposited. This is repeated until 
the crystals obtained are 10-12 cm. in length In fact, commerce 
seeks rather to have large and regular crystals than pure ones. 
The crystals are removed, washed with a small amount of water, 
and dried. 

Sometimes the salt is crystallized in groups by suspending crystals 
to threads tied to wooden rods placed in the crystallizing- vats. 

As to the very fine crystals, they are dissolved in water, and, 
after concentrating the solution to 30 B., allowed to crystallize; 
the salt thus obtained is added to the crude salt and treated as 
such. The mother liquors, evaporated to 40 B., yield pearly crystals 
of a double salt of cyanide and chloride of potassium, much used 
in the manufacture of alum. 

The refined salt is never pure: it always contains a little potas- 
sium sulphate which is difficult to get rid of. Yet one may obtain 
it free from sulphate by dissolving the salt in water and concen- 
trating the solution to the density 1.31. At this point the greater 
part of the sulphate of potash separates out. Water is then added 
to bring the density to 1.27 and the solution allowed to crystallize. 
This is done but rarely, for the presence of potassium sulphate does 





not in any way interfere with the industrial use of potassium ferro- 
cyanide, the only objection being that it reduces by just so much 
the amount of useful cyanogen. 

The manufacture of potassium ferrocyanide leaves behind two 
important residues: a black mass and blue potash. 

The black mass is made up of the residue from lixiviating the 
metal. It is friable and of a composition varying according to the 
nature of the organic substances used and the method of procedure 
It consists to a large extent of carbon and mineral substances- 
silicates, phosphates, chlorides, sulphides, soda, potash, lime, etc. 

In the following table Karmrodt gives the analyses of three 
samples of this black mass: 






Per Cent. 
6 10 

Per Cent. 

Per Cent. 
4 22 










2 15 


1 27 

Sesquioxid and metallic iron 

4 80 

14 17 

10 24 







. 02 (?) 



21 14 

26 45 

29 70 

Sulphuric acid 

1 27 

1 85 


Phosphoric acid 

10 45 

4 92 

6 44 

Residue : Sulphur, CO 2 ; chlorine, CN 







The amount of the black mass varies according to the substances 
used. Karmrodt found the following: 

Using wool wastes 28. 3% 

" horn 18.7 

" hair. 23.0 

" leather scraps 35. 

It is sold mostly as a fertilizer, due to its high content of potash 
and phosphoric acid. In order to recover the potash (9%), vari- 
ous uses have been attempted, especially that of utilizing it in the 
manufacture of alum, but the experiments thus undertaken were 
not successful owing to the fact that the labor cost more than the 
value of the product. 



Blue potash is the residue after evaporating to dryness the 
mother-liquors obtained from the crystallization of the crude salt. 
It contains potash in excess in the free state or in the form of salts 
not combined with cyanogen, and the salts supplied by the ash, 
It is used again in the process, mixed with fresh potash. Its 
composition varies according to the number of ignitions to which 
it has been subjected. It is evident that it becomes more and more 
impure, and ends by becoming useless. 




Potassium carbonate. . . 
' ' silicate. . . . 

44.1 to 84.0 
7. 6 to 20.4 





1.4to 8.8 


6 18 


7.2to 13.1 



2 04 


4 34 


7 22 


2 84 



Insoluble residue 
Other substances 

1 26.77 j 

2 1 


Theory of the Manufacture of Potassium Ferrocyanide by the 
Old Process. Seyeral hypotheses have been proposed on this sub- 
ject, the first and most probable of which is the following: 

Nitrogenous organic substances contain carbon, nitrogen, hydro- 
gen, and oxygen. After ignition, they still contain all these elements 
except oxygen and a large part of the nitrogen which is volatilized in 
the form of ammonia. Now as the amount of carbon in these sub- 
stances is much larger than that of nitrogen, it follows that only a 
part of this carbon enters into combination with the nitrogen in order 
to yield cyanogen, 

and the rest of the carbon reacts upon the carbonate of potash, 
which it reduces, thus setting the metal free, 

= C0 2 +CO+K 2 , 


which metal, reacting upon the cyanogen formed, unites with it and 
produces potassium cyanide, 

CN+K = CNK. 

As may be seen, iron seems to take no part in this reaction, and yet 
it is indispensable that some be put in. In fact, carbonate of potash 
always contains, besides other impurities, a small amount of sulphate 
of potash. In contact with carbon, this salt becomes likewise 
reduced, yielding potassium sulphide, 

S0 4 K 2 + 4C = K 2 S+4CO, 

and this sulphide, in the presence of the cyanide formed, yields 

The object of the iron is, therefore, to absorb the sulphur of the 
potassium sulphide, forming insoluble iron sulphide, 

K 2 S+Fe=FeS+K 2 , 

K 2 S + Fe + 2C + 2N = FeS + 2CNK, 

which entirely prevents the formation of sulphocyanide, the forma- 
tion of which must, under all circumstances, be avoided in the 
manufacture of potassium ferrocyanide. 

Therefore the product after igniting the raw materials (nitrog- 
enous subst nces, carbonate of potash, iron), otherwise called the 
metal, will be a rather complex mixture which may contain: 

Potassium cyanide; 

Alkali carbonate in excess; 

Undecomposed organic substances; 

Iron ; 

Iron sulphide; 


It should be stated that we do not include the presence of potas- 
sium ferrocyanide in the said mixture. It is, in fact, admitted, 
according to actual data, that this salt is formed only at the time of 
lixiviation in the following way: 


During lixiviation, potassium cyanide reacts with sulphide of 
iron, yielding potassium ferrocyanide according to either of the 
following reactions: 

2CNK+Fe = (CN) 2 Fe+K 2 
4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 , 


2CNK + FeS - (CN) 2 Fe + K 2 S 
(CN) 2 Fe +4CNK = Fe(CN) 6 K 4 , 


6CNK + FeS = K 2 S + Fe(CN) 6 K 4 . 

That is precisely the reason why one should not think of extracting 
directly by lixiviation the potassium cyanide formed in the "metal." 
Still another theory is the following:* The reason for igniting 
organic substances is to produce a nitrogenous charcoal which 
would react with the potassium carbonate, yielding, in all proba- 
bility, acetylene. In its turn the acetylene would react with the 
potassium, set free from potassium carbonate, and with the ni- 
trogen of the organic substance, or, in case of need, with nitrogen 
of air, thus yielding potassium cyanide, as follows: 

C 2 H 2 + K 2 + N 2 = 2CNK + H 2 . 

It is just at this point that the presence of iron would cause the 
formation, first of cyanide of iron, then of potassium ferrocyanide, 
according to the reactions above indicated. 

Yield. The yield obtained by igniting nitrogenous organic 
substances depends on several conditions. 

From many experiments on a large scale made by Karmrodt, it 
follows that the yield may vary from 10-18% of the weight of the 
salt used. 

As an average of 459 different operations, Fleck places the yield 
at 11%. 

Hoffmann studied the various conditions which may influence 
the yield, the following being the result of his investigations: 

(1) The nature of the nitrogenous organic substances exerts a 

* Prunier, Medicaments chimiques, Vol. I. 


considerable influence on the yield of cyanide and of sulphocyanide; 
it is, however, impossible to. establish a fixed relation between the 
yield and the nitrogenous content of the organic substances used. 

(2) The formation of potassium cyanide 'is quite closely pro- 
portional to the weight of organic substances. 

(3) The yield seems to increase with the purity of the alkali. 

(4) The yield increases especially with the temperature. 

(5) It increases more rapidly still if for a like quantity of potash 
the addition of organic substances be increased. 

(6) If blue potash be employed, the amount of black mass is 
twice as great as if pure potash had been used. 

(7) For the same amount of potassium ferrocyanide produced, 
the amount of pure potash consumed depends on the nature of the 
organic substances. 

(8) The comsumption of organic substances is greater with blue 
potash than with pure potash. 

(9) The amount of sulphocyanide formed does not vary whether 
iron shavings or iron turnings be added to the mixture ; but it decreases 
if finely divided reduced iron be used; there is almost no forma- 
tion if at the end of the operation forge scales be added. To these 
theoretical considerations should be added the following, based 
upon experimental data: 

(1) A relatively small proportion (Vs- 1 /?) of the total nitrogen 
of the organic substances contributes to the formation of the cyanide. 
The remaining 4 / 5 or 6 /7 ar e lost or volatilized as ammonia. A 
certain amount is, however, retained. At the beginning of ignition, 
the temperature being relatively low, a portion of the nitrogen 
escapes under the form of ammonia; but when the temperature has 
become raised, this ammonia coming in contact with carbon becomes 
converted into hydrogen and hyrdocyanic acid, which latter unites 
with potassium in order to form cyanide of potassium. It follows 
that if this high temperature could be obtained from the beginning 
of the operation, there would probably be formation 'of cyanide 
from the first. 

(2) Just as only a small proportion of the total nitrogen be- 
comes really utilized, so only a fraction of the potash used unites 
with the cyanogen. According to Karmrodt's experiments, this 
amounts to l / 7 - 1 /io. It should, however, be remarked that besides 


'its role of absorbing the cyanogen formed, potash also acts as a 
flux, the effect of which is to reduce the mass to a state of liquid 
which is absolutely indispensable for the proper formation of potas- 
sium cyanide. Part of the potash is recovered in the mother-liquors, 
but a rather large amount is volatilized or lost in the various manipu- 
lations. According to Hoffmann this loss may amount to 10-20%. 
(3) Besides cyanide of potassium there is also formed during 
ignition sulphocyanide of potassium. The formation of this salt 
is variously explained. According to some it is due to the presence of 
potassium sulphate in the carbonate used. Hoffmann objects to 
his hypothesis because when in his experiments he used potash 
absolutely free from sulphate, he noticed a formation of sulpho- 
cyanide to about the same extent. These investigations led 
to a second hypothesis: the influence of the sulphur, which is 
present almost always in animal substances, the amount reaching 
sometimes 3%. A great portion of this sulphur is, however, vola- 
tilized, the rest being converted into sulphocyanide. In fact this 
formation of sulphocyanide constitutes a loss from the point of view 
of the yield of ferrocyanide, a loss which may amount to 1 / 5 of its 
weight. It is for the purpose of overcoming this objection that 
iron is added, which during the fusion reduces the sulphocyanide. 
If, however, one succeeds in the laboratory in obtaining a metal 
free from sulphocyanide, it is entirely different on an industrial 
scale, in which case a small amount of this salt is always found. N611- 
ner recommended the use of chalk, but the results obtained with 
this reagent .are not very satisfactory. Forge scales give excellent 
results, but they have the great objection of breaking up a portion 
of the potassium cyanide. All in all, iron is the best reagent; it 
also serves in preventing a too rapid wear and tear of the apparatus; 
it unites with the potassium sulphide and converts it into iron sul- 
phide, which does not attack the walls of the vessels. 

K 2 S+Fe=FeS+K 2 . 

(4) The reaction should not be carried on too far, otherwise 
the yield may decrease 9-12% (Hoffmann). 

(5) The substances employed should all be absolutely dry, the 
water-vapor set free during the reaction exerting an action which 
decomposes the cyanide formed. 


Observations Concerning Lixiviation and Crystallization. (1) The 
use of iron protoxid salts to convert cyanide into ferrocyanide is 
advantageous. The carbonate or sulphate of iron may be used, 
but generally in the industries the use of sulphide of iron is pre- 

(2) In evaporating the lyes, it is best not to bring them imme- 
diately to the boiling-point, otherwise the unconverted cyanide 
of potassium woUd be decomposed. The temperature should 
not exceed 70-80. Brunquell recommends macerating the metal 
during 24 hours at 50-60. 

The sum total of these various theoretical and practical considera- 
tions shows well that the manufacture of potassium ferrocyanide 
by the old process is filled with defects and requires a great deal of 
care if a really profitable yield is to be obtained. All in all, the 
losses are considerable and intimately bound to numerous circum- 
stances. The chief objections to this method may be thus summed up : 

(1) Serious losses of nitrogen through volatilization at the time 
of ignition. 

(2) Loss of potash. 

(3) Loss of cyanide because of the formation of sulphocyanide 
and cyanate. 

(4) Loss of cyanide due to the incomplete transformation of 
this salt at the time of lixiviation. 

(5) Rapid wear and tear of the apparatus. 

(6) Heavy expense for fuel. 

It has been sought to remedy these objections, and numerous 
improvements have been applied to the methods which we have just 

The object of most of them is to utilize, as much as possible, 
the nitrogen, which at the beginning of ignition escapes from the 
organic substances under the form of ammonia. Such are the 
processes of Brunquell and of Karmrodt. 

BrunquelTs Process. This process may be carried out in two 
different ways. 

In the first, two iron retorts are used connected with a vertical 
tube. The mixture of organic substances, potash, and iron prepared 
in the ordinary manner is charged into the lower retort, while the 
upper retort contains a mixture of animal charcoal and potash. 


These two retorts are placed in a specially constructed furnace. 
First the upper retort is heated to bright redness, and then the 
lower retort is so heated as to bring the mass to a state of 

In BrunquelPs second improvement, only one cylinder is used, 
the lower half of which is filled with the ordinary mixture and the 
upper half with charcoal and potash. This cylinder is suspended 
by a chain and may be raised or lowered at will into a vat-like fur- 
nace which is provided with a grate containing a hole through which 
the cylinder may pass. At the beginning of the operation the 
cylinder is lowered deep enough so that only the upper part is sub- 
jected to the heat; when this part has reached the desired tempera- 
ture, the cylinder is raised so that it is found completely in the 
furnace and consequently heated on all sides. 

In this way, in the first as well as in the second apparatus, the 
gases set free by the mixture of the lower .part passed through the 
upper mixture. Notwithstanding these advantages Brunquell's two 
processes have never been adopted on an industrial scale. 

Still another improvement, due to Brunquell, consists in con- 
verting most of the nitrogen into volatile products by means of 
repeated distillations with lime, then to utilize the ammoniacal 
products thus obtained for the manufacture of ferrocyanide by 
passing them through a series of cylinders filled with charcoal and 
potash heated to bright redness. The ammonium cyanide thus 
formed is collected in a strong solution of sulphate of iron. Cyanide 
of iron is formed, which when boiled with potash is converted into 
potassium ferrocyanide. For a certain time this process was tried 
in France, with this modification, however, that the ammonium 
cyanide was absorbed by a strong solution of potash to which a 
salt of iron had been added. 

Karmrodt's Process. Along the same line, Karmrodt's process 
should also be mentioned. The object of this process is the same 
as that of Brunquell, and it may profitably be combined with the 
manufacture of animal black. The apparatus used consists of 
two parts, the carbonization vessel and a cylinder charged with 
wood charcoal impregnated with potash. The two parts are con- 
nected by means of a tube. The cylinder, which is vertical, is pro- 
vided with a fire-grate; one begins heating the cylinder by means 


of this fire-grate. With the aid of a special appliance the prod- 
ucts of combustion are conducted either into the main chimney 
or into a flue joined to the carbonizing retort. When the cylinder 
has reached the temperature of redness, the gases of the fire-grate 
are conducted under the carbonizing retort. The volatile prod- 
ucts here liberated pass through the connecting tube into and 
through the cylinder. 

The yield is appreciably greater than by the ordinary process, 
but it is, nevertheless, far from the theoretical yield, which the 
whole of the ammoniacal products set free should give. 

Several processes for the conversion of sulpho cyanides into 
ferrocyanides have been invented, among which only two deserve 
to be taken into consideration. 

Conroy's Process. The first is that of Conroy, Hurter, and 
Brock (1896). It consists in treating the crude sulphocyanide 
with a solution of ferric or ferrous chloride. The mixture is heated 
to 270-280, in an autoclave provided with a stirrer, in the pres- 
ence of an excess of iron, preferably reduced iron. 

The sulphocyanide is converted into a mixture of ferrocyanide 
and sulphide of iron, which is collected, washed, and finally decom- 
posed with a caustic alkali. The residue from the treatment with 
alkali, consisting of a mixture of sulphide of iron and ferric and 
ferrous hydrate, is treated with hydrochloric acid, which forms iron 
chloride, which may be used anew. The hydrogen sulphide thus 
liberated is collected and used. 

Musspratt's Process. The second process is that of H. E. Hether- 
ington and E. K Musspratt (English patent No. 5830, March 20, 

It consists in treating a sulphocyanide of an alkali or alkaline 
earth with metallic iron. First finely divided iron (filings, turn- 
ings, or iron sponge) is heated with tar, the object being to reduce 
the oxid which always forms on the surface of these products. The 
iron thus prepared is mixed with sulphocyanide and tar in the follow- 
ing proportions: 

Reduced iron 70-80 parts 

Tar 20-40 " 

Sulphocyanide of potassium or sodium 100 " 


This mixture is heated to 350 F. in a closed vessel connected 
by a tube to a condensation retort. This retort serves in condens- 
ing the sulphocyanide which might be volatilized during the opera- 

The product of the reaction consists of a mixture of alkali ferro- 
cyanide, iron and alkali sulphides, and tarry residue. It is treated 
with hot water, the solution thus obtained being treated with car- 
bonic acid, which removes the hydrogen sulphide, and then 
concentrated to crystallization. In case of ferrocyanide of sodium, 
it is best to concentrate directly. 

Goerlich and Wichmann's Process. This process (German pat- 
ent No. 9139, Aug. 4, 1894, March 11, 1895) is practically the same. 

It consists in fusing alkali sulphocyanide with iron and treating 
the product of fusion, before lixiviation, with a current of moist air 
mixed with carbonic acid. In this way ferrocyanide, sulphur, 
alkali sulphide, and carbonate are obtained: 

2[K 6 (CN) 6 -6FeS]+170 + 21H 2 0+2C0 2 

=2K 4 Fe(CN) 6 .3H 2 0+2C0 3 K 2 +5Fe 2 (OH) 6 4-12S. 

By this process almost the whole of the sulphur is removed, and 
alkali carbonate is obtained instead of alkali sulphide. 

In the absence of carbonic acid, the reaction is as follows : 

2K 6 (CN) 6 - 6FeS + 150+ 21H 2 

=2K4Fe(CN) 6 -3H 2 0+ 2K 2 S +5Fe 2 (OH) 6 +10S. 

The oxidized product is treated with water, and the soluble salts are 
separated by fractional crystallization. The residue may be used 
in recovering metallic iron. 

Process of the Works du Castelet. Lastly, we will mention the 
extremely original process described in the patent No. 308808 of 
March 8, 1901, taken by La Societe des Usines du Castelet, and 

It consists in causing a gaseous mixture of J acetylene and f 
ammonia to act, at a nascent red heat, upon an intimate mixture 


of oxid, carbonate, or hydrate of iron and alkali oxid in a closed 
vessel. The reaction is as follows: 

6 C 2 H 2 + 12NH 3 + 8KOH + Fe 2 3 = 2Fe(CN) 6 K 4 + HH 2 + 34H. 

The product is dissolved in boiling water, the clear solution being 
decanted, evaporated, and allowed to crystallize on cooling. 


The manufacture of illuminating-gas has made great strides in 
the last thirty years in England, Germany, and in France. Thus 
the annual consumption of gas in England reaches almost 3000 
million cubic meters; in France it is about 700 million cubic 

As will be seen later, the cyanide compounds exist already formed 
in the gas. It is therefore quite natural that one should think of 
reaping some advantage from it. To be sure, the percentage is 
quite small, and sometimes even trifling; but on the other hand, 
if one thinks of the enormous quantity of gas annually produced 
in the different countries, one can easily conceive how the gas 
industry may offer a profitable source of cyanide production. 

Further, it should be stated that cyanogen is an injurious product 
which it is necessary to remove before delivering the gas for con- 
sumption. It decreases the illuminating power perceptibly, and 
is a toxic product. Besides its being absolutely necessary to remove 
it from the gas, there is profit in its recovery. 

In England the question of cyanides in the manufacture of gas 
has keenly prejudiced the mind, and the manufacturers and investi- 
gators have foreseen the advantage to be derived in these sub- 
stances in a country so rich in coal and gas. Germany is not at all 
behind in this respect, there being few gas-works which do not recover 
the cyanide compounds. 

On the other hand, France has shown but little interest in this 
question, and even at the present time there seems little disposi- 
tion to extend this industry. 


Moreover, it is a fact to be regretted that in France so little 
importance, and sometimes even not any at all, is attached to the 
by-products of certain manufactures. It is not a rare sight, indeed, 
to see numerous works neglecting such an interesting and often 
remunerative question as the recovery of by-products. Thus, for 
example, in the case of illuminating-gas, there are to our knowledge 
works of importance which do not even condescend to take the 
trouble to purify the gas, or if they are compelled to do this because 
of hygienic statutes, do not get any profit out of their sluice waters 
or from their spent oxid. 

And yet in most cases the recovery and utilization of by-prod- 
ucts (especially in the industry which we are discussing) require 
but slight costs of installation, costs which are repaid by the profits 
obtained and by a better quality of product, which is the chief ob- 
ject of the manufacturer. It should also be stated that the process 
of recovering these by-products does not generally modify the 
carrying on of the operations. 

Thus, if one considers that in France the manufacture of illu- 
minating-gas requires annually about 4,000,000 tons of coal, and 
that from each ton one can extract cyanide compounds worth 2-3 
francs, it is easily seen that the illuminating-gas industry could 
recover, each year, a profit of 8 to 12 million francs, which is not 
at all an amount to be neglected. 

One objection may be interposed to the above remarks, and that 
is, that in France many gas-works are of but slight importance, 
and under the circumstances the recovery of these by-products 
seems to offer no benefit considering the small amount of product to 
be treated. To this objection the following reply may be made: 
Most of the gas-works are in the hands of powerful companies often 
possessing a large number of works. It would be a simple matter 
for each works to recover the cyanide compounds, and to obtain 
concentrated products (e.g., masses rich in cyanide) which might 
be profitably transported to a central works, which could be espe- 
cially occupied with the treatment of by-products furnished by all 
the works of the company. The expense would be slight and large 
profits would be assured. 

From all the foregoing remarks it follows that the gas industry 
may with advantage prove a source of production of cyanide com- 


pounds, a production which would require but little expense if it 
were well understood, and which under these conditions would 
almost suffice for the demand in the cyanides. 

There is therefore, every reason, and it is also necessary, that the 
cyanide compounds should be recovered from the gas, and one should 
encourage every gas-manufacturer so to do. 

We shall now study the various ways proposed to bring about 
this operation profitably, but before that it seems necessary to 
mention briefly in what the manufacture of illuminating-gas con- 

As is well known, illuminating-gas is a product of the distilla- 
tion of coal in closed vessels. Coal used in the manufacture of 
gas is the dry smiths' coal burning with a long flame, and contain- 
ing the following percentage composition (water and ash free) : 


The principal types of coal most commonly used are those 
from Nord, Pas-de-Calais, Mons, the Sarre, Ruhr, and New- 
castle. This distillation takes place in retorts, formerly made 
of cast iron, but now of refractory brick, arranged ordinarily 
in a series of seven or nine, in a furnace which is heated either 
directly with coke or by means of combustible gases produced 
"by a gas-generator placed under the furnace for the recovery of 
the heat. These retorts, whose dimensions vary with the size of 
the works, are heated to a temperature of about 1100. The result- 
ing gas consists of a very complex mixture of different products 
(volatile and non-volatile hydrocarbons, ammonia, and ammoniacal 
salts, hydrosulphuric and hydrocyanic acids). Thus obtained, this 
product is unfit for domestic use, and must therefore be subjected 
to purification. The object of this purification is to separate the 
products, which on account of their easy condensation would befoul 


and obstruct the pipes, or which on account of their own character- 
istics would considerably decrease the illuminating power of the 
gas, or would constitute a source of danger to the health of the 
consumers on account of their noxious properties. 

The purification of gas is carried on in two stages: the first 
is purely physical, whereas the second is based on chemical 

The physical purification consists in removing all the easily 
liquefiable or condensable products; the chemical purification 
consists in absorbing all the harmful substances which escape the 
physical by means of certain definite substances. The method 
of procedure is as follows: 

On emerging from the retorts the gas passes into a horizontal 
cylindrical apparatus half filled with water into which cylinder 
outlet tubes. from all the retorts converge. The level of the water 
is kept constant by means of an overflow. The gas abandons in 
this apparatus the less volatile products (tars) and a portion of 
the ammonia. From there the gas goes to a collector, a very long 
horizontal tube about 0.80 metre in diameter, where a great part 
of the light tars that have escaped the previous treatment are 
deposited. Then it goes into a condenser or cooler consisting of 
a system of inverted U tubes, joined to a rectangular box, divided 
into sections by partitions, into which the condensed products 
are collected (water-vapor, ammoniacal salts, ammonia, and the 
tars which have escaped the first and second treatment).. The last 
traces of these products are removed in the scrubber, a tall cast- 
iron cylinder consisting of two chambers filled with coke and into 
which a thin stream of water flows in a direction opposite to that 
of the incoming gas. Finally by passing the gas through the 
Pelouze and Audouin condenser the last traces of tar are removed,, 
and it only remains to subject the gas to the second stage for 
chemical purification. For this purpose the gas passes into a 
series of boxes filled with a mixture of sawdust, ferric oxid, lime, 
and sulphate of lime, which absorbs the ammonia, carbonic, 
hydrosulphuric, hydrocyanic, sulphocyanic acids, etc. When this 
mixture no longer exerts any purifying action, it is " revivified " 
by spreading and stirring it in the air, when it may be used 


As may be seen by this short sketch the manufacture of gas 
yields many different products which may be divided as follows: 





( Ammonium carbonate (NH 4 ) 8 CO 




More illuminating ele- 

Elements which affect 
the purity of the gas 

Ammonium sulphide 

r Ammonium chlorid NH 4 C1 

< Ammonium cyanide NH 4 CN 

( Ammonium sulphocyanide NH 4 CNS 



Acetylene C 2 H 2 

Ethylene C 2 H 4 

Propylene C^H 6 

Butylene C 4 H 8 

Allylene C 3 H 4 

Crotonylene C 4 H 6 

Terrene C 6 H 8 

Benzol C 6 H 6 

Thiophene C 4 H 4 S 

Styrolene C 8 H 8 

Naphthalene Ci H 8 

Methylnaphthalene CnHi 

Acetylnaphthalene C, 2 Hi 

Fluorene CuH 10 

Fluoranthane Ci 5 Hi 

Propyl C 3 H 7 

Butyl C 4 H tt 

f Hydrogen H 2 

| Methane CH 4 

I Carbon monoxid CO 

Carbonic acid CO 2 

Ammonia NH 8 

Cyanogen CN 

Sulphocyanogen CNS 

Methylcyanide C2H 3 N 

Hydrogen sulphide H,S 

Sulphide of carbon CS 2 

Sulphides of the hydrocarbons 

Oxysulphide of carbon COS 

Nitrogen N 





Varying in composition according to the nature of the mixture used, but 
generally containing: 

Sulphate of ammonia, 
Ferrocyanide of ammonia, 
Sulpho cyanide of ammonia , 
Cyanide of ammonia, 
Prussian blue, 
Sulphide of iron, 
Oxid of iron, 
Sawdust, tar, etc. 

The amounts vary according to the kind of coal used, but, as 
a rule, from 100 klgm. of coal the following are obtained: 

I. Coke 70 klgm. =1.8 hectoliters 

II. Gas 30 cu. m. D = 0.4 

III. Tar. '. 3J to 6 klgm. D = 1.2 

IV. Ammoniacal liquors 6-9 klgm. 1 to 8 Baume 

(corresponding to 1-5% pure ammonia) 

Of these various products three only are of interest, because 
they contain cyanide compounds, namely: 

1. Gas itself. 

2. Ammoniacal liquors. 

3. Purifying materials. 

We shall take up these three substances one after the other, 
in order to extract from the products of the distillation of coal 
the cyanide derivatives which they may contain, and which quite 
naturally vary according to the nature and the composition of the 
raw material used, and according to the methods of conducting 
the distillation. 

But before taking up the extraction of cyanides in the manu- 
facture of gas it would seem indispensable to review the various 
theories set forth concerning the formation of these compounds 
and the reactions which may produce them. 

Cyanide compounds are naturally formed in the production of 
illuminating-gas, and they may be found, in the various stages of 
the manufacture, in the following forms: Cyanogen, sulphocy- 


anogen, sulphocyanic acid, hydrocyanic acid, cyanide, ferrocyanide, 
sulphocyanide of ammonium, etc. 

The nitrogen necessary for the formation of these compounds 
comes from the coal, which, according to the character of the coal 
used, contains various amounts. 

% Kind of Coal. 

Per Cent N. 


Haut-fleau ("fat ") 


de Marsilly 





Bracquignies ("half -fat") 


Mariemont ........ 


Valenciennes ("fat ") 












Bousquet d'Orb 


Sables (washed) 


Trelys " 


Tre"lys (crude) 


Martinet (washed) 


Fontanes ' ' 




Ch. MSne" 

Rouchamp, 1. . 



" 2 


i ( 

" 3 




Poirier ("fat") 

1 375 

de Marsillv 

Carabinier (French) 

1 00 

it y 

Bois d'Heignes 



Three-quarter vein 

1 65 


Beg vein 

1 47 

(Lab'y of Mines, London) 

Low " 

2 05 


1 84 

Doul in (South), Wales 

1 28 


1 32 


1 69 


2 05 


1 1 

2 37 

Ch Me"ne" 

South of Wales coal 

1 65 

n ii t ( it 

1 49 

Lancashire (uninflammable) 

1 93 

Scotland " 

2 09 

ft tt 

1 33 

1 1 1 1 

1 57 

" "speakcoal" 

1 20 

Cannel-coal-Wigan (Lancashire) 

2 12 

' ' Tyneside (Newcastle) . . 

1 85 


Anthracite (South Wales) 










Kind of Coal. 

Per Cent N. 





Alien wald ' ' 


Hernitz " 


Friedrichsthal " 




Konigshiitte (Prussia) 


Schwachhof er 

Morgenstern ' ' 


Hermenegilde (Low Silesia) 



Carolinen (Prussia) 


Jaklowetz (Low Silesia) .... . . 


Waterloo (Prussia) 



1 00 



1 50 


1 45 



1 87 


1 20 



1 06 


From the foregoing table, the average content of nitrogen in 
coal may be seen to be 1 to 1.6%. 

The distillation of coal distributes this nitrogen among the vari- 
ous products formed, and only a small proportion passes into the 
state of cyanide compounds. 

Forster studied the migration of nitrogen produced during the 
distillation of coal in closed vessels (Journal of Gas Lighting, 
1882). One of his experiments was made with a coal containing 
1.73% nitrogen; and this he found distributed as follows: 
0.251 or 14.50% passes into ammonia 
0.027 or 1.56% " " cyanogen 

0.863 or 49.90% remains in the coke [state 

0.589 or 34.04% passes into the tars, and into the gas in a gaseous 
1.73 100.00 

Knublauch, who repeated the same experiment on three samples 
of coal, found: 

Total nitrogen of the coal 1 . 555 

Nitrogen in the coke 0. 466 

Nitrogen in the gas 0. 856 

Nitrogen in the form of ammonia 0. 185 

Nitrogen " " " " cyanogen 0.0268 

Nitrogen in the tars 0.0212 





1.555 1.479 1.17a 


Or for for every 100 parts of nitrogen contained in the coal, there are 

i. 2. 3. 

JSfitrogen in the coke 30.0 35.6 63.9 

" " gas 55.0 47.1 21.1 

" " form of ammonia 11.9 14.1 11.6 

" " " " ll cyanogen 1.8 1.8 1.8 

" " tar 1.3 1.4 1.3 

100.0 100.0 100.0 

Leybolt (Journal fur Gasbeleuchtung, 1890) gives the following 
results : 

Coke 31. to 36. % 

Ammonia 10. to 14. % 

Cyanogen 1.5to 2. % 

Tar ,. l.Oto 1.3% 

Gas 46 . to 56 . 0% 

Guegen (Journal du gaz et de Pelectricite 1884) likewise 
studied the distribution of the nitrogen in the products of the 
distillation of two coals, carried on at 900 in sandstone retorts. 

Nitrogen in the form of ammonia 

Nitrogen in the form of cyanogen in the tar and in 

the gaseous products 

Nitrogen in the coke 


Coal from Grand- 

Buisson, Mons, 


Coal from Li6vin. 

Distribution of 100 Parts Nitrogen. 







These figures are not at all absolute: they vary with the nature 
of the coal, the method of operation in the works, the temperature 
of the distillation, etc., yet they show that the amount of cyanide 
compounds formed is relatively small, and that it can only become 
of value when large quantities of coal are treated. 


Cyanogen is therefore always formed in very small quantities 
in the distillation of coal. The amount formed depends much on the 
temperature of the distillation, cyanogen not being formed except 
in brisk distillations carried on at a high temperature. In distilling 
coal at a higher temperature, Foulis of Glasgow found that 2831 
liters of gas yielded 6.5 grams of cyanogen, while when working at 
a low temperature this amount was cut down to less than half. Accord- 
ing to Hunt, the most favorable temperature is 950 and above, 
while at 700 to 800 one would obtain only one twelfth as much 
cyanogen. This remark is, moreover, confirmed by the experi- 
mental fact that the greatest part of the cyanogen is formed 
toward the end of the distillation that is, at the moment when the 
temperature is the highest, and at this very moment the quantity 
of ammonia formed is very small. 

A small yield of cyanogen therefore accompanies a large yield 
of ammonia, and vice versa. 

Perthuis carried out a series of experiments which show this 
to be true, and that the yield of cyanogen reaches its maximum at 
the end of the distillation, while at the beginning it is almost nothing: 

Length of Hydrocyanic Acid Retained by 

Distillation. 100 Cu. M. of Gas. 

1-2 hours trace 

3-4 " 77.1 grams 

5-6 " 142.1 " 

The form in which the cyanogen comes out of the distillation 
retorts has given rise to many discussions, and the opinions ex- 
pressed relative to this subject vary greatly. 

According to some investigators, cyanogen occurs in the gas in 
the form of cyanide and sulphocyanide of ammonium. 

The reaction would be that indicated by Kuhlmann: 

C + 2NH 3 =CN-NH 4 +H 2 . 

When this ammonium cyanide comes in contact with sulphur 
and sulphide of carbon in the highly heated retort it becomes par- 
tially transformed into ammonium sulphocyanide. 

But, on the other hand, the experiments of Bergmann clearly 
prove that the action of ammonia on carbon or on carbon monoxid 


at a red, heat does not yield ammonium cyanide, but hydrocyanic 
acid, according to the reaction 

C+NH 8 CNH+H a . 

According to Lewis, and this is the most probable opinion, the 
cyanogen found in gas may exist therein only in the form of free 
cyanogen or free hydrocyanic acid. Lewis bases his views upon the 
following principles: (1) It is impossible that cyanogen should 
exist in the gas in the form of sulphocyanic acid (CNSH), for this 
latter in the presence of hydrogen becomes decomposed into hydro- 
cyanic acid and hydrogen sulphide: 

CNSH + 2H = CNH+H 2 S. 

(2) Neither can it exist under the form of ammonium cyanide f 
since this salt is decomposed from the time the temperature exceeds 
26.6 C. 

(3) It is also quite improbable that it occurs therein in the state 
of ammonium sulphocyanide, experiments having clearly proven 

Finally, other investigators admit that ammonium cyanide is 
formed, but that it becomes decomposed by carbonic acid con- 
tained in the gas, this decomposition yielding hydrocyanic acid 
and ammonium carbonate. This would of course explain the 
absence of ammonium cyanide in the scrubbers. 

However that may be the formation of cyanogen compounds 
in gas takes place in the distillation retorts at a high temperature; 
it probably results from the action of ammonia on carbon or on 
carbon monoxid at a high temperature. This reaction in all 
probability causes the formation of free hydrocyanic acid, which 
in the course of its passage through the series of apparatus becomes 
transformed, as will be seen. 

In the ammoniacal liquors, cyanogen is found principally under 
two forms: as ferrocyanide and sulphocyanide of ammonium. 
Ammonium cyanide exists therein but rarely and in a subsidiary 

According to Lewis, ammonium ferrocyanide will be formed by 
the action of free hydrocyanic acid, in the presence of ammonia. 


on iron sulphide, which is itself formed by the action of hydrogen 
sulphide on the iron framework of the condenser: 

6CNH + 6NH 3 +FeS=Fe(CN) 6 (NH 4 ) 4 +(NH 4 ) 2 S. 

The ammonium ferrocyanide cannot in any way come from the 
iron contained in the coal, nor be formed in the retorts because 
all the ferrocyanides are decomposable at temperatures much lower 
than those reached in the retorts. 

As to the ammonium sulphocyanide, its origin is a little more 
obscure and still requires some elucidation. 

And yet Lewis thinks, from experiments, that it results from 
the action of carbon bisulphide on ammonium sulphide, 

(NH 4 ) 2 S + CS 2 = 2H 2 + CNS NH 4 , 

this sulphide of carbon being itself produced by the action of the 
sulphur of pyrites contained in the coal on the carbon at the tem- 
perature of the distillation. 

The amount of ferrocyanide and of sulphocyanide of ammonium 
found in ammoniacal liquors is relatively very small. Lewis estimates 
that on an average 181 grams of ferrocyanide of ammonium, cal- 
culated as Prussian blue, is found in one ton of coal, and of sulpho- 
cyanide of ammonium he found 226 to 907 grams per ton of distilled 

As the result of experiments carried on in certain German works 
at Wiesbaden, Karlsruhe, Mainz Esop gives the following 
figures (Chemische Industrie, 1892, page 116). 

Ppr PpTit Ammonia in the 

Ammoniacal Liquors. 

Sulphocyanic acid 1 .22 18.05% 

" 1.51 19.03% 

" " 2.33 36.05% 

Lunge claims that the quantity of sulphocyanide of ammonium 
contained in the ammoniacal liquors in the manufacture of gas in 
England amounts to 11 kilos per 454 liters; but Clayfield after 
numerous experiments was able to find but 0.453 kilo per 454 


It is not at all surprising that the ferrocyanide and the sulpho 
cyanide of ammonium, both very soluble in water, should exist in 
such small quantities in the ammoniacal liquors; this is due simply 
to the action of carbonic acid which displaces the hydrocyanic and 
the sulpho cyanic acids from their combinations. 

On the other hand, in the purifying materials the cyanogen is 
retained almost wholly, and if we consult the following table by 
Lewis, it will easily be seen that immediately after passing through 
the first purifier the quantity of cyanogen compounds contained 
in the gas diminishes considerably, and that it is in this first purifier 
that the greater portion of the cyanogen products formed during the 
manufacture are collected. 

Hydrocyanic Acid 
per Cubic Meter. 

After the retorfs 19 . 2 to 30. 6 grams. 

" " condensers 18.9 to 29.0 

11 " scrubbers 18.4 to 18.8 

" " 1st purifier 1.2 to 14.2 

" " 2d " 0.5 to 1.2 

" "3d " 0.45 to 0.50 gram. 

" "4th " 0.30to 0.40 " 

Leybold had, moreover, made similar experiments, showing the 
progressive elimination of cyanogen, with the following results: 

Hydrocyanic Acid Hydrocyanic Acid, 

per 100 Cu. M. Per Cent. 

I. II. I. II. ' 

Conduit 265.9 203.4 5.4 14.57 

After condensation 251 . 6 173 . 6 45 . 09 

/' 1st purifier 131.7 

'" 2d " 83.3 59.5 18.2 56.15 

" 3d " 61.6 8.16 

In the gasometer 41.2 19.8 15.5 9.73 

The purifying materials are, as is known, composed of a mixture 
.of ferric hydrate and sulphate of lime, obtained by the reaction of 
Abime on sulphate of iron; this mixture is then made porous with 

The gas, on coming into the purifying boxes, contains the follow- 
ing impurities: Hydrogen sulphide, ammonia and cyanogen com- 


pounds. Rather complex reactions take place in the purifiers 
between the purifying materials and the impurities, there being 
formed notably ferrous cyanide, ferrocyanide of iron and ammonium,, 
carbonyl ferrocyanide of sodium, and ammonium sulphocyanide. 

The formation of ferrocyanide may be explained in various ways. 

The hydrocyanic acid would react on oxid of iron in order to 
form ferrous cyanide, which in the presence of oxygen of the air 
would become converted into Prussian blue : 

Fe 2 3 +4CNH = 2Fe(CN) 2 +2H 2 0+0, 

9Fe(CN) 2 + 3 = Fe 2 3 + Fe 7 (CN) 18 . 

It follows, however, from Leybold's experiments that if a current 
of hydrocyanic acid mixed with hyrdogen be passed through the 
purifying materials no absorption takes place, while, on the other 
hand, if the purifying materials be first saturated with hydrogen 
sulphide the hydrocyanic acid becomes entirely combined, due to 
the previous formation of iron sulphide, according to the reaction 

FeS +2CNH = H 2 S +Fe(CN) 2 , 

the ferrous cyanide formed then becoming converted into Prussian 
blue under the action of atmospheric oxygen. 

Other investigators claim that the ferrous cyanide results from 
the action of ammonium cyanide on oxid or sulphide of iron. 

FeO +2CN NH 4 = Fe(CN) 2 + (NH 4 ) 2 

FeS + 2CN . NH 4 = Fe(CN) 2 + (NH 4 ) 2 S, 

and if ammonium cyanide be in excess there is formation of am- 
monium ferrocyanide: 

Fe(CN) 2 +4CN -NH 4 =Fe(CN) 6 - (NH 4 ) 4 . 

In every case it is to be noted that Prussian blue is not formed 
directly in the purifiers, but by oxidation of the ferrocyanide. 
Moisture or the use of steam facilitates the formation of ferrocy- 
anides, whereas ammonia prevents it. It is therefore of the utmost 


importance, if one wishes to obtain materials rich in ferrocyanide, 
to wash the gas as completely as possible, in order to remove the 
ammonia. By removing the ammonia almost entirely, Knublauch 
succeeded in obtaining materials containing up to 24% of ferro- 
cyanide of potassium (reckoned on the dry matter). 

In fact ammonia, oddly enough, facilitates the formation of 
sulphocyanide of ammonium or of sulphocyanide of iron. Knublauch 
in 1877 was the first to show the close relation which exists between 
ammonia and sulphocyanogen, and he showed how the sulphocy- 
anides may be formed at the expense of ferrocyanides if the washing 
of the gas has been insufficient. 

Sulphocyanide of ammonium exists in but very small quantities 
in gas as it comes to the purifying boxes, but it may be formed 
in large amounts in these boxes, especially if ammonia or ammonium 
sulphide are found in the presence of finely divided sulphur such 
as exists in the spent oxids or in the presence of hydrogen sulphide. 

According to Lewis the reactions which take place on the forma- 
tion of sulphocyanide are as follows: 

NH 3 + CNH + H 2 S = CNS NH 4 + H 2 , 

Fe 2 S 3 + CNH = CNSH + 2FeS ; 
CNH + H 2 S + = CNSH -f H 2 0. 

Leybold studied this phenomenon and analyzed two purifying 
masses saturated with hydrogen sulphide which had been sub- 
jected to the action of a mixture (1) of hydrocyanic acid and am- 
monia and (2) hydrocyanic acid and ammonium sulphide: 

I. II. 

CNH + NH 3 . CNH + (NH 4 ) 2 S. 

Water 23.60% 33.02% 

Sulphur . .... 24.98% 11.39% 

Prussian blue 1 .70% 5.38% 

Ammonium sulphocyanide 3 . 03% 4 . 40% 

Ammonia 2.05% 0.75% 

It results from these analyses that, in the case of ammonia, 
the amount of sulphocyanide formed is, as is known, greater than 
that of Prussian blue, and that in the case of ammonium sulphide 
it is about equal. 


The presence of an alkali in the purifying materials is likewise 
very favorable to the formation of the sulphocyanides. 

During the "revivification" of these materials, if care be not 
taken to avoid heating, the formation of sulphocyanides at the 
expense of ferrocyanides is considerable. Burschell estimates that 
it may sometimes amount to 30% of the weight of ferrocyanides. 
This transformation is due to the action of ammonia and of hydrogen 
sulphide found in the purifying materials, and to the moisture con- 
tained therein, and likewise to the action of sulphur and the alkali 
sulphides on the ferrocyanides. 

As may be seen from this rapid review of the complicated reac- 
tions which control the formation of cyanogen compounds in the 
gas itself, in the ammoniacal liquors and in the purifying materials, 
this formation is intimately dependent upon numerous conditions. 
The gas-worker who is desirous of recovering the cyanogen should 
strive to avoid or to produce them according as they are injurious 
or favorable. 

We shall now take up the various processes which the manu- 
facturer may put into operation in order to extract the cyanide 

A. In the illuminating-gas. 

B. In the ammoniacal liquors. 

C. In the spent oxid. 


Although the presence of cyanogen compounds in gas has been 
known for a long time (it is mentioned in an English patent in 1850), 
it is only within the last few years, on account of its limited use 
in the arts, that any attempt has been made to derive any benefit 
from it. The spent purifying materials, or Laming's mixture, were 
considered as valueless waste products, and it was not till 1880 
that a French manufacturer, Gauthier-Bouchard, thought of utiliz- 
ing them for the manufacture of Prussian blue and of potassium 
ferrocyanide. As these cyanogen compounds are formed naturally 
in these materials, and without care or thought on the part of the 
manufacturer, this process has been but little improved. But from 
the time that cyanides became useful in the treatment of aurifer- 


ous minerals, many investigators, especially in Germany, perceived 
the possibility of making gas a profitable source of cyanide pro- 
duction, and sought to extract from gas the greatest amount of 
cyanide possible. They soon recognized that Laming's mixture, 
or other similar materials, were but an imperfect and expensive 
source of production. In fact it is easily understood that this 
treatment in the dry way has the disadvantage, notwithstanding 
the porosity which sawdust gives to the mixture, of presenting 
but a small contact action to the cyanogen and its compounds, 
and that the absorption of these bodies is necessarily incomplete. 
Moreover it has already been noticed that on account of secondary 
reactions appreciable amounts of sulphocyanides may be formed 
in the materials, which are of less value than are the ferrocyanides, 
and their subsequent conversion into cyanides is more difficult. 

These are the reasons which caused the investigators to seek 
the extraction of the cyanogen compounds as completely as possible 
directly from gas. At present these processes seem to prevail 
among gas manufacturers who are anxious to derive some benefit 
from such an important by-product, while in the works which, 
for some groundless reason, persist in refusing to consider the impor- 
tance of cyanides in gas, the purifying materials are still being worked 
for the Prussian blue, in order to make of it a better commercial 

In other works, and they are numerous enough, they do not 
even try to obtain materials rich in f errocyanides ; and when these 
materials are spent, i.e. do not absorb any more hydrogen sulphide, 
they are sold to manufacturers of Prussian blue or of cyanides. 

In Germany and England processes for direct extraction of 
cyanides from gas are established on a large scale, and it is to be 
hoped that the French will not long remain behind their neighbors. 

The ideal method of direct extraction of cyanide compounds 
from illuminating-gas as it comes from the retorts would be to 
pass it through an alkaline solution, thus forming an alkali cyanide 
But this is quite impossible on account of the presence in gas of 
other acid gases, e.g. carbonic acid and sulphuric acid which could 
immediately displace hydrocyanic acid and therefore prevent all 
formation of cyanide. Therefore the idea of obtaining cyanides 
directly from gas must be abandoned. 


Combinations upon which carbonic acid and hydrogen sulphide 
have no action must be sought. 

Knublauch J s Process.. Knublauch was the first investigator to 
become interested in this important question. Knublauch, who 
since 1877 had undertaken a whole series of researches on cyanogen 
in illuminating-gas was led during his experiments to find a method 
which allowed direct extraction of the cyanogen products from gas 
in a wet way (German patent No. 41930, Aug. 18, 1886 ; French 
patent No. 209770, Nov. 25, 1890). 

This process consists in passing the gas into purifiers, washers, or 
scrubbers containing in solution one or more of the substances men- 
tioned in the two following groups: (1) alkalis, ammonia, ammoni- 
acal liquors, alkaline earths, magnesia, carbonates and sulphites of" 
these bases ; (2) iron, manganese, zinc, oxids, hydrates, or carbon-- 
ates (natural or artificial) of these metals. 

Knublauch noticed that carbonic acid and sulphhydric acid did' 
not in any way interfere, and that even when these two gases were 
found in large quantity in the gaseous mixture, at the moment of 
passing through a solution containing both iron and an alkali, 
cyanogen forms with them ferrocyanide with so great an energy 
that the affinity of carbonic acid and hydrogen sulphide toward 
cyanogen is so weakened as to render the amount of hydrogen sul- 
phide absorbed insignificant. 

The gas should always pass through a liquid and not a solid mass,, 
and this liquid should be agitated during the passage of the gas, 
which passes through successively a series of absorption apparatus 
so arranged as to permit easy change of the order of succession. 

If, for example, a gas, such as illuminating-gas, containing, besides 
cyanogen, carbonic acid and hydrogen sulphide be passed into a 
solution containing a ferrous salt and an alkali, the precipitated 
ferrous hydrate, Fe(OH) 2 disappears almost wholly in the state of 
soluble alkali ferrocyanide, while only a small portion remains in. 
suspension in the liquid in the form of sulphide of iron. If an amount 
of iron greater than that of alkali be used, an insoluble cyanide is 

The amount of absorbent material to be used for a definite weight 
of cyanogen depends on the nature of these materials, and the 
proportions naturally vary as one uses mono or bivalent bases, 


hydrates or carbonates, natural or artificial products. In general, 
for every molecule of hydrocyanic acid, a molecule of alkali, of 
alkaline earth, hydrate or carbonate, and somewhat less than a 
molecule of iron compounds should be used. The quantity of 
liquid used should at least be sufficient to allow the gas to bubble 

Knublauch's method has received but few trials in England. 
Its want of success was due not to the results which it yielded but 
to the lack of interest shown by the manufacturers, at the time of 
its appearance, for the direct recovery of cyanogen. 

Gasch's Process. The process of Robert Gasch of Mainz (patent 
No. 201377, Dec. 24, 1889) consists in using recently precipitated me- 
tallic sulphides, which with the cyanogen of the gas form a ferrocya^ 
'nide. The indispensable condition is the presence of ammonia, which 
condition is found in illuminating-gas. The higher the temperature 
the more rapid and complete is the conversion. It is instantaneous 
at from 50 to 60. The action of the heat may be suppressed when 
the reaction is well begun, and this can be done by adding a cyanide 
precipitate obtained from a cyanide solution coming from a previous 
operation. The operation is carried on by means of ordinary 
washers, or by the means of vertical boilers, which allow intimate 
contact of the gas with the absorbent materials, and this apparatus 
is so placed that the gas which passes through it has a temperature 
not exceeding 36, a temperature at which sulphocyanides begin 
to be formed. 

According to the author of this process, its advantages are as 
follows : 

(1) An increased yield in ammonium ferrocyanide. 

(2) High concentration and purity of the cyanide liquors under 
a form suitable for further treatment. 

(3) The only impurities are a- small amount of ammonium and 
potassium sulphides. 

Gasch recommends, moreover, the use of liquids holding in sus- 
pension a metallic sulphide such as iron sulphide, to which is added 
a milk of lime, and having in solution a soluble salt (oxalate or 
sulphate of alkali, an ammonia salt, sulphate of magnesia, aluminum, 
iron, etc.). 

If, for example, a solution of sodium sulphate be used to which 


is added a milk of lime and having in suspension sulphide of iron, 
a weak solution of sodium ferrocyanide will be obtained contain- 
ing more or less sodium sulphide and a deposit of sulphate of 
lime and sulphide of calcium, both insoluble. 

Rowland's Process. This process (French patent No. 218215 r 
March 21, 1892) consists essentially in having the ammoniacal 
liquors of the scrubber absorb the whole or greater part of the cyano- 
gen. For this purpose Rowland adds an iron salt to the water 
of the scrubber in suitable quantity, but not in such quantity that 
iron sulphide will be formed. The optimum amount is 5.5%. 
Ammonium ferrocyanide is formed which remains in solution. After 
the addition of a fresh quantity of salt or oxid of iron, the ammo- 
niacal liquors are distilled, the addition of iron converting the ammo- 
nium ferrocyanide into double ferrocyanide of iron and ammo- 
nium, which is insoluble and may be separated from the liquor 
by adding milk of lime and filtering. The filtered solution is heated 
to boiling and sulphate or chloride of potassium is added, thus form- 
ing a double ferrocyanide of potassium and lime. The same result 
may be obtained by acidifying the liquor and boiling. The double 
ferrocyanide of potassium and lime is treated with potassium car- 
bonate, which on ignition converts it into alkali ferrocyanide and 
carbonate of lime. A strong solution is made and allowed to crys- 

Fowlis' Process. Fowlis of Glasgow has patented a process 
(English patent No. 9474, May 18, 1892) which is similar. The gas, 
previously freed of ammonia, is passed through a solution of potas- 
sium or sodium carbonate containing oxid of iron (Fe20s) or car- 
bonate of iron in suspension. This solution is prepared as follows: 
To 25 liters of a solution of ferrous chloride (FeCb), containing 
150 grams Fe per liter, is added a solution of 7.5 kg. carbonate of 
sodium at 98 in 150 liters water. Carbonate of iron is precipitated, 
the solution of sodium chloride is decanted, and the carbonate of 
iron is put in suspension in a solution of 13.5 kg. of carbonate of 
sodium in 200 liters of water. The 13.5 kg. of carbonate of sodium 
may be replaced by 17.5 kg. carbonate of potassium. A scrubber 
provided with several horizontal plates is best suited for this opera- 
tion. These plates are perforated with numerous small holes, upon 
which rest tubes covered with a cap forming a hydraulic closing, 


as in the distillation columns. The absorbent mixture, contained 
in a cylinder which is provided with stirrers, flows regularly or in 
;an intermittent manner into the scrubber. It comes to the tubes, 
falls from one compartment to another, and finally flows through 
;the lower part of the apparatus. In circulating in this way it meets 
the gas, which flows in the opposite direction, the cyanogen of the 
gas being thus removed. 

The ferrocyanide solution is evaporated to dryness, the tar and 
other impurities accompanying it being easily removed by redis- 
solving. The clear solution is concentrated and allowed to crys- 

Speaking concerning Fowlis' process before the English Gas 
Congress in 1896, Charles Hunt stated that he produces a solution 
of sodium ferrocyanide which on concentration and crystallization 
gives 75% sodium ferrocyanide. One must acknowledge that that 
is already a splendid result setting well in relief the profit which 
may be gained by the direct extraction of cyanogen from gas. 

Claus and Domeier's Process. This process (1895-96) is but a 
modification of Fowlis' method. These investigators first pre- 
pare an absorbent material by fusing a mixture of iron or oxid of 
iron, sulphate of sodium or potassium, and charcoal. The product 
of fusion, taken up with water, yields a grayish-black substance, 
slightly soluble, being a compound of iron and the alkali metal 
Fe 2 Na 2 S3. This substance is suspended in water and placed in a 
series of washers, into which the gas, previously freed of ammonia, 
passes. Ferrocyanide and sulphocyanide of sodium are formed. 
This process does not form much of the latter salt. 

Schroeder's Process. Schroeder proposes to collect all the cya- 
nogen compounds into the ammoniacal liquors (French patent No. 
281456). To the waters which are used in absorbing the ammonia, 
ferrous chloride is added. When the gas passes through this solu- 
tion, the ammonia of the gas forms a precipitate of iron hydrate, 
Fe(OH)2, and ammonium chloride; then the hydrogen sulphide 
. converts the hydrated oxid of iron into sulphide of iron, which remains 
. suspended in the absorption waters with oxid of iron; these are 
dissolved by the ammonium cyanide of the gas, which converts 
..them into ammonium ferrocyanide. 

The liquid is distilled in the presence of milk of lime, the ammonia 


being thus recovered. Calcium ferrocyanide, slightly soluble, is 
in part precipitated. To obtain the calcium ferrocyanide still in 
solution a current of gas freed of ammonia and cyanogen is con- 
ducted through the solution, the carbonic acid precipitating the 
lime. The small amount of calcium ferrocyanide still remaining 
in solution may be precipitated as Prussian blue by means of a 
solution of iron perchloride. The precipitate, consisting of cal- 
cium ferrocyanide, Prussian blue, and carbonate of lime, is then 
heated to boiling and treated, with constant stirring, with potassa 
or potassium carbonate so as to convert the calcium ferrocyanide 
and the Prussian blue into potassium ferrocyanide, which, being 
soluble, may be separated from the insoluble carbonate of lime 
by filtration. The filtered solution is then concentrated and allowed 
to crystallize. 

Teichmann's Process. This process is also based on analogous 
reactions (French patent No. 290265, June 28, 1890), but instead -of 
using the chloride, this investigator uses the sulphate of iron, and 
in case of need he employs zinc solutions. In using iron sulphate 
in the washers, this salt becomes at once converted, by means of 
hydrogen sulphide and ammonia, into iron sulphide and ammo- 
nium sulphide. Then the cyanide of ammonium acts on the iron 
sulphide, yielding ammonium ferrocyanide. 

The greater portion of the cyanogen thus goes into solution, 
while a small part of it remains insoluble in the form of cyanide 
of iron. Sulphide of iron dissolves just as fast as ammonium cyanide 
is absorbed, and by repeated additions of a solution of iron sulphate, 
solutions containing a high percentage of ammonium ferrocyanide 
may be obtained. 

The absorption apparatus may be inserted between the tar 
extractor and the apparatus used in absorbing the ammonia. With- 
out fear of obstruction, the ordinary scrubbers or the standard 
washers may be used. But, when working on a large scale, it is best 
to place the iron solutions in the washers. 

The solutions of ammonium ferrocyanide obtained may be pre- 
cipitated by means of calcium chloride. 

The reaction is the same when zinc salts are used. The pre- 
cipitated zinc sulphide is converted by the ammonium cyanide into 
the double cyanide of ammonium and zinc and ammonium sulphide. 


By the addition of other zinc salts to the solution of the double 
cyanide, zinc cyanide may be precipitated which may be converted 
directly into potassium cyanide. 

Lewis* Process. The last process to be mentioned in this class 
is that by Lewis (Moniteur Industriel, 1897, Nos. 26 and 27). This 
is based likewise on the affinity which cyanogen or hydrocyanic acid 
has for sulphide of iron held in suspension in an alkaline solution, 
the object of the process being to obtain a ferrocyanide. 

Lewis recommends that the process be carried on as follows: 

The sulphide of iron is produced by precipitating an iron salt by 
means of a. liquid prepared with the waste gases in the treatment 
of ammonia. 

The sulphide of iron is held in suspension in a specially con- 
structed washer, containing an alkaline solution in which is an 
excess of soluble iron. 

The washer should be so constructed as to aljow intimate contact 
of gas with the suspended iron, and to avoid the formation of a 
modified ferrocyanide, K 7 Fe(CN)i 2 , which is less stable. 

The ammonia should be removed as thoroughly as possible from 
the gas before the latter be allowed to enter the washer, since the 
acids of the fixed ammoniacal salts, e.g., ammonium chloride, forms, 
with the alkali, an alkaline chloride which contaminates the product 

By working carefully and with an efficient system of washers 
the reaction should theoretically be as follows: 

2C0 3 K 2 + FeS + (CNH) 6 = K 4 Fe(CN) 6 + H 2 S + 2C0 2 + 2H 2 0. 

But in reality, as Lewis has stated, there are formed complicated 
and involved inter-reactions. 

That is the chief defect of all the processes which have been 
reviewed. Their perfect operation depends on numerous conditions 
chemical as well as mechanical or physical, which influence the 
results to a very large extent, and unless great care and many pre- 
cautions be taken in operating these processes, they will be far from 
being successful. Moreover, these processes all have the disadvan- 
tage of producing but very dilute solutions most of the time, and 
the cost of treating such large quantities of liquids is heavy. These 


are the reasons why these methods have received but limited trials,, 
and have never been applied on a large scale. 

Bueb's Process. The process invented by J. Bueb, several years 
ago, is entirely different. This process, now in operation by the 
Deutsche Continental Gas Gesellschaft of Dessau, has thus far 
produced very favorable results. This method will be studied 
somewhat more at length, because it is at present in operation, and 
because of all the methods for the direct extraction of cyanogen 
from gas this is almost the only one which deserves to be kept in 

In fact, the reactions utilized by Bueb are those mentioned in 
the processes of Knublauch and others, but with this difference, 
that instead of ' seeking to produce a soluble f errocyanide Bueb 
produces an insoluble compound. 

The principle of this process consists in bringing the gas, pre- 
viously freed of tar, into intimate contact with a saturated solution 
of sulphate of iron. The ammonia of the gas, playing the role of 
the alkalis, used in the other processes, a compound of iron, cyano- 
gen, and ammonium is formed, which separates in the form of a 
light mud. 

In practice, the operation takes place in an apparatus specially 
constructed by Bueb on the same principles as the standard 
washers, with this difference, that instead of flowing automatically 
into the apparatus the washing liquid passes, at definite intervals, 
from one chamber to another by means of a pump near the washer. 
The sulphate of iron solution, previously prepared in a special mixer ^ 
is pumped into the last of the four chambers, then from this one 
to the one preceding, and so on to the first chamber. The cyanogen 
muds, obtained in the first compartment of the washer, are col- 
lected into a forged iron reservoir or into a special vat, to be trans- 
ferred to suitable vessels if they are to be sold as such, or to be 
latertreated in the works itself, according to processes which will 
be mentioned further on. The first three compartments are 
provided with revolving discs similar to those of the standard 
washers, while the fourth has a stirrer, the object of which is to 
avoid the thickening which takes place in this chamber. 

As these cyanogen muds obtained by this process contain appre- 
ciable amounts of ammonia they may be treated for the extrac- 


tion of this product, especially if the works have a plant for their 
treatment. To this end the muds are heated to boiling by means 
of direct steam in boilers provided with stirrers. The gas thus 
liberated passes into a cooler where the ammonia condenses whereas 
the sulphide vapors are conducted into a purifier. The residue is 
subjected to the action of a filter-press in order to separate the 
solution of ammonium sulphate from the insoluble cyanogen product. 
The ammonium sulphate solution which flows from the filter is 
concentrated and allowed to crystallize. The insoluble residue, 
which is a blue mass containing about 30% Prussian blue (44% 
ferrocyanide of potassium), and 4% ammonia, is put in tuns or 
sacks and sold as such. 

In communications made to two successive annual Congresses 
of the German Gas Industries (Kassel, 1899; Mainz, 1900) Bueb 
gives the following details concerning the working of his process: 

The concentrated solution of iron sulphate introduced into 
the last compartment should show about 20 B. (That is, should 
contain 28% FeS0 4 + 7H 2 0.) In this compartment, which is that 
of the gas outlet, the gas contains only traces of cyanogen, but 
contains ammonia and hydrogen sulphide, which, coming in con- 
tact with the iron sulphate, converts it completely in 6 to 10 hours 
into sulphide of iron and ammonium sulphate: 

FeS0 4 + H 2 S+2NH 3 =FeS + (NH 4 ) 2 S0 4 . 

On reaching the other compartments this solution of ammonium 
sulphate, holding sulphide of iron in suspension, meets the gases 
which are richer and richer in cyanogen and ammonia, and these 
two bodies reacting on the sulphide of iron form with it an insoluble 
double salt (NH 4 ) 2 Fe(CN) 6 , while hydrogen sulphide is set free, 
and is carried out of the washer, or remains in part in the product 
of the reaction in the form of ammonium sulphide: 

2FeS+6CN.NH 4 = (NH 4 ) 2 Fe(CN) 6 +2(NH 4 ) 2 S. 

This reaction is finished completely in the first compartment 
of the washer. 

The reaction in its various stages may, moreover, be followed 
by the coloration of the absorbent material. In the last compart- 
ment, which contains the ir^n solution, the liquid is black; it becomes 


lighter in the others, and in the first it is greenish yellow. The 
cyanogen mud which results from this operation contains an 
amount of cyanogen equal to 18.2% of potassium ferrocyanide 
(Fe(CN) 6 K 4 +3H 2 0) and to 12.2 to 13.5% of Prussian blue, besides 
j6 to 7% of ammonia, an amount which represents about one third 
of the ammonia obtained hi gas-works. 

If some double salt still remains in solution it may be made 
insoluble by simply boiling and without the addition of any reagent. 
The yield by this process is 95% of the cyanogen, but the results 
depend much on the kind of coal used. 

The English coals are those which contain the most cyanogen. 
They yield 7.4 grams of potassium ferrocyanide (Fe(CN)6K4+3Il20) 
per cubic meter of gas. In a plant where a mixture of English and 
Upper Silesian coal is used 5.3 grams are extracted per cubic meter 
of gas. In another works using a mixture of English and Westpha- 
lian coal the yield was 5.6 grams. The coals of the Saar give a 
yield of 4 to 4.5 grams; those of the north of France 4 to 5 grams; 
those of the east 4 grams; in general the minimum is 3.5 grams 
and the maximum is 8 grams. 

Furthermore, Bueb's process allows a very simple removal of 
hydrogen sulphide. Cyanogen possessing the property of decom- 
posing the sulphide of iron recently formed by setting hydrogen 
sulphide free, it is evident, as Bueb points out, that this property 
would thwart the absorption of hydrogen sulphide by the purifying 
materials, which, according to the old processes, should play the 
double role of absorbing cyanogen and hydrogen sulphide. There- 
fore, purifying materials are obtained containing 50-60% of 

Bueb has, moreover, observed that his process gives a larger 
yield the warmer his gas is, that is, that the gas is cooled less before 
it passes through the absorption apparatus. For this purpose 
instead of placing the coolers, as is usual, before the cyanogen sepa- 
rators, Bueb places them next to these, i.e., between them and 
the scrubbers. In this way a smaller amount of ammonia remains 
in the cyanogen absorption apparatus, and because of this the 
yield in cyanogen compounds is again increased. Another advantage 
of this new arrangement is that at the high temperature at which 
the gas is kept the last traces of tar and naphthalene are easily 


removed; and to this end Bueb places another vessel filled with: 
oil before the cyanogen 'absorption apparatus and connected with 
it. This oil, being heated by the passing gases, absorbs more easily, 
at this temperature, a larger amount of tar and naphthalene. 

Bueb's process marks a real progress in the extraction of cyanogen 
from gas, even considering only the results obtained: Thus in the 
dry way only 50-60% of the cyanogen present in gas could be 
extracted in well-conducted operations, while by this new process 
the yield is quantitative. Moreover, the cyanogen may be recovered 
in a very practical shape, since these products are obtained in such 
concentrated form as to warrant the expense of transportation, 
provided the gas-maker does not care to convert them into cyanide. 

A. Smits of Amsterdam, without knowing beforehand the inves- 
tigations of Bueb, in an interesting communication to the Inter- 
national Congress of Gas Industries in 1900, confirms the results 
obtained by the latter at Dessau by his own experiments made 
at the gas-works at Amsterdam according to a process similar to 
that of Bueb. 

Smits mentions here the reasons which led him to absorb hydro- 
cyanic acid in the presence of ammonia (loc. cit) instead of bring- 
ing the gas previously freed of ammonia in contact with a solu- 
tion of potassium carbonate holding a ferrous salt in suspension: 

"It is remarkable that generally the absence of ammonia has 
been considered as a condition indispensable for a good absorption 
of hydrocyanic acid. I suppose that we have been led into error 
by the following phenomenon: When illuminating-gas, coming in 
contact with the absorbent liquid, contains ammonia analysis shows 
a less amount of yellow prussiate of potash in the clarified solution, 
but after having again analyzed the black precipitate, which is always 
formed during absorption, it is easily proven that this precipitate 
contains a quantity of cyanogen which is proportional to the amount 
of ammonia which the gas contained, whence it follows that the 
total amount of hydrocyanic acid absorbed is in this case greater. 

" Now then, in this way an amount of hydrocyanic acid is 
obtained, which would be lost during absorption in the ammonia 

" Again, the presence of ammonia helps the formation of an in- 
soluble cyanide, and that is the reason why a smaller amount of 


yellow prussiate of potash ie formed in the liquid in the presence 
of ammonia." 

" Those are the reasons which led me to suppose that the place 
where hydrocyanic acid was being absorbed was badly chosen." 

Starting with these facts, Smits sought to absorb the hydro- 
cyanic acid by means of a ferrous sulphate solution at the exit of 
an apparatus where the gas still contains large quantities of am- 
monia, and like Bueb, he was able to prove that the yield was 
quant ative. 

Thus, as may be seen, the problem of the direct extraction of 
cyanogen from illuminating-gas is really simple, and at the same 
time profitable, since it permits the extraction of this cyanogen 
almost in its entirety. 

Feld's Process. Finally shall be mentioned the process for the 
direct extraction of cyanogen from gas, just recently patented by 
Feld (French patent No. 317382, Sept. 1901), and which certainly 
does not lack in originality. 

It consists in absorbing the cyanogen in such form that it may 
then be recovered by simply heating to boiling, in the state of pure 
hydrocyanic acid, which may then be absorbed by ordinary reagents 
whereas the impurities of the gas are either previously removed 
or are in great part unabsorbed. 

Feld divides the substances capable of absorbing cyanogen under 
these conditions into three groups : 

First group. Basic or carbonated compounds, which in aqueous 
solutions, or in suspension in water or salt solution, absorb hydro- 
cyanic acid, and afterwa d give it off on boiling. These are com- 
pounds of magnesium, aluminium, zinc, manganese, and lead. They 
may further be divided into three subgroups: 

(a) Those which absorb CNH and C0 2 and leave H 2 S. These 
:are basic compounds of magnesium. 

(6) Those which absorb CNH, but neither C0 2 nor H 2 S. These 
are the basic compounds of aluminium and magnesium carbonate. 

(c) Those which absorb CNH and H 2 S but not C0 2 . (Basic 
compounds of zinc, manganese, and lead.) 

Second group. Compounds which in basic, neutral, or acid 
solution, or in suspension in water or in saline or acid solution, 
absorb hydrocyanic acid, and give it up completely on boiling only 


in the presence of acid. To this group belong the compounds of 
copper, mercury, and the ferric and ferrous salts. The iron com- 
pounds give up the hydrocyanic acid completely only when they 
are not intermixed. 

Third group. Compounds which when hot even in basic solution 
or in suspension in water, and in the presence of salts of the first 
group, do not absorb hydrocyanic acid, but decompose hydro- 
sulphuric acid. 

In this group are included ferric and ferrous salts either separate 
or mixed. 


As we have seen at the beginning of this chapter, the ammoniacal 
liquors contain a certain amount of cyanogen in the form of ferro- 
cyanide and sulphocyanide of ammonium. The amount of the 
former varies, on an average, from 150-180 grams, calculated as 
Prussian blue, per ton of coal. The amount of ammonium sulpho- 
cyanide present in ammoniacal liquors is quite variable, and depends 
much on the length of time they have been stored. Thus, in the 
same liquors, Lewis found 1.76, 3.5, and 4 grams sulphocyanide 
at intervals of one month. Generally one ton of spent gas-liquors r 
that is, having been subjected to distillation of ammonia, yields, on. 
an average, 6 kg., of ammonium sulphocyanide. 

Formerly the operation was carried on as follows: After the 
gas-liquors had been distilled in the presence of lime in order to 
recover the ammonia, they were allowed to stand, and to the clear 
solution were added equal amounts of copper sulphate and iron 
sulphate. Copper sulphocyanide was thus formed, which was 
decomposed by means of ammonium sulphide with formation of 
ammonium sulphocyanide (Spence's process). 

Later the ammonium sulphide was replaced by barium sulphide. 

Pendrie's Process. The object of this invention (French patent 
No. 189648, March 28, 1888) is to recover the cyanogen compounds 
of the ammoniacal liquors in the form of Prussian blue. 

The residues, after the distillation of the ammonia, are allowed 
to stand until clarified and then decanted. Ordinary sulphuric 
acid is then added to acid reaction in order to remove any hydrogen 


sulphide contained therein. A portion of the hydrogen sulphide 
is set free, another portion is decomposed. The whole is allowed 
to stand 24 hours, during which the sulphur and sulphate of lime 
settle. The solution is decanted, and to the liquid is added a suit- 
able quantity of a ferric salt, Prussian blue being precipitated 
This may be converted into potassium ferrocyanide, after having 
first decanted the solution, and allowing the Prussian blue to stand 
in contact several days, with a lye made of caustic potash or potas- 
sium carbonate. 

Bower's Process. Bower (German patent of Dec. 23, 1895), 
recommends the precipitation of ferrocyanides and sulphocyanides, 
by means of a copper salt in order to form insoluble ferrocyanide 
and sulphocyanide of copper. A mixture of these two salts, when 
treated with iron, yields on the one hand insoluble ferrocyanide 
of iron, and on the other soluble sulphocyanide, which may there- 
fore be easily separated. In practice Bower recommends carrying 
on the process as follows: 

Before distilling, the ammoniacal liquors are treated with mag- 
netic iron either alone or with the addition of an iron salt, in suffi- 
cient quantity to convert all the cyanogen into the form of ferro- 
cyanide and sulphocyanide of iron. 

The liquors are then distilled in the presence of quicklime in 
a boiler provided with a stirrer. The residual liquors, containing* 
ferrocyanide and sulphocyanide of calcium, are then treated with 
a solution of cuprous chloride in sufficient quantity to precipitate 
the whole of the cyanogen compounds as insoluble salts. 

The precipitate is collected, washed, and, while still moist, treated 
with finely divided iron. The iron replaces tne copper, yielding 
insoluble ferrocyanide, and soluble sulphocyanide. These ara 
separated by filtration. 

The ferrocyanide of iron is then treated at the boiling-point^ 
with an alkali, in order to obtain a soluble alkali ferrocyanide, which 
is purified by crystallization. The solution of sulphocyanide is. 
concentrated and allowed to crystallize. 

Lewis' Process. Somewhat different is the process of Lewis 
and Cripps (English patent No. 5184, March 7, 1896), the method of 
procedure of which is as follows: After distilling off the ammonia 
by the usual method with lime, the residual liquors contain the 


ferrocyanide and the sulphocyanide in the form of lime salts 
(CNS) 2 CaandCa 2 Fe(CN) 6 . This liquor flows from the stills into 
a suction reservoir whence a pump drives it to the top of a tower, 
filled with pieces of coke or brick, through which it filters, encounter- 
ing on its way down an inverse current of sulphurous acid and car- 
bonic acid, which is obtained by passing the waste gases of an ammo- 
nia distillation over a grate which burns the hydrogen sulphide 
and converts it into sulphurous acid. The action of this gaseous 
current neutralizes and acidifies the originally alkaline liquid. On 
emerging from the tower the acid solution flows into a long reservoir 
divided into two unequal compartments. The solution first comes 
to the larger compartment where it is treated with a solution con- 
taining ferrous and ferric salts in order to precipitate the ferro- 
cyanide as Prussian blue. The liquid passes from one compart- 
ment into the other, thus allowing the Prussian blue precipitate 
time in which to settle. The supernatant liquid then flows into 
a special reservoir, there to be treated with a view to the recovery 
of the sulphocyanides. 

For this purpose a copper sulphate solution is added to the 
liquid, there being formed an insoluble white precipitate of cuprous 

Ca(CNS) 2 +S0 3 H 2 +2CuS0 4 + H 2 =Cu 2 (CNS) 2 +CaS0 4 +2H 2 S0 4 . 

The previous treatment with sulphurous acid is absolutely necessary, 
otherwise there would be formed a partially soluble black copper 

The cuprous sulphocyanide precipitate is separated by decanta- 
tion and washed. It is treated with a solution of alkali sulphydrate 
which forms a soluble alkali sulphocyanide and an insoluble copper 
sulphide. The alkali hydrosulphate is likewise obtained by utilizing 
the waste gas of an ammonia distillation, these gases passing through 
a washer filled with a strong caustic alkali solution. When the 
copper sulphide is exposed to air and then treated with an acid, the 
copper salt employed in the precipitation is "revivified/ and may 
be used over again. 



The purifying materials which are used for the chemical purifica- 
tion of gas still constitute, in the works where the direct extraction 
of the cyanide compounds is not in operation (arid they are the 
larger number) , an important source of these products. As has already 
been seen, these materials contain almost the whole of the cyanogen 
formed during the manufacture of gas, and it has likewise been 
shown that the other impurities, especially hydrogen sulphide, are 
also absorbed therein. 

The composition of the purifying materials varies in different 
works and in different countries. Generally mixtures of lime and 
ferrous sulphate or oxid of iron are still used. In Germany and in 
Belgium, purifying materials are used on a large scale, composed 
entirely of artificial oxids of iron, especially the brown oxid, known 
under the name of limonite. The hydrated and moist oxid seems 
to be preferable for the absorption. Below the composition of two 
limonites is given: 

I. II. 

Holland. Belgium. 

Sesquioxid of iron 51 . 30 59 . 14 

Alumina 1 . 17 0. 98 

Lime and magnesia 1 . 63 . 59 

Silica 4.97 5.23 

Organic substances 26 . 26 19 . 64 

Water 14.02 15.13 

Loss and undetermined 0. 63 1 . 09 

These purifying materials are converted, on account of the 
passage of gas through them, into sulphur, sulphide of iron, ferrous 
ferrocyanide, sulphocyanide of iron, etc., and the moment neces- 
sarily arrives when they become inactive. In order to revivify 
them they are spread out on a flat surface, where they are constantly 
stirred with a shovel. The oxygen of the air converts the inactive 
sulphide of iron into the active oxid and sulphur, 

and the ferrous ferrocyanide into Prussian blue. The same mix- 
ture may be revivified several times, the result being that an appre- 


ciable part of the oxid of iron becomes converted into Prussian 
blue (which may be recognized by the greenish-blue color which 
the materials assume) and the sulphur accumulates in such quan- 
tities (30 to 40%) that the mixture no longer exerts any purifying 

It is hi this 'state that it is known as spent oxid, which is immedi- 
ately treated or more generally sold to manufacturers of Prussian 
blue or of prussiates. 

Its composition varies naturally according to a great many 
circumstances: kind of coal distilled, method of distillation, the 
composition of the purifying materials, the degree of fineness of 
the same, the method of revivification, etc. 

According to Esop, the sulphocyanic content varies from 0.39 
to 4.25%, the potassium ferrocyanide from 3.02 to 4.58%, the 
ammonia from 0.49 to 4.38%. Below are given some analyses of 
purifying materials. 


Sulphur 41.79% 

Prussian blue 7.37 

Sulphocyanic acid 3.01 

Hydroferrocyanic acid 1.01 


Sulphur 40.75% 

Prussian blue 3.08 

Ammonium sulphocyanide 5. 14 

Ammonia 2. 23 


I. II. 

Sulphur 30.58% 30.03% 

Prussian blue 6.30 8.62 

Ammonium sulphocyanide 4.08 2. 12 

Ammonia 0.41 1.30 

Formerly the spent oxids were considered as useless residues, 
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and to-day they are treated with a view to the extraction frcm 
them of sulphur ammonium sulphate 'and cyanogen compounds. 

Gauthier-Bouchard's Process. To Gauthier-Bouchard is due 
the idea of utilizing the purifying materials for the manufacture 
of potassium ferrocyanide. This process, which was set up in a 
works at Aubervilliers, was operated as follows: 

The materials were first subjected to lixiviation with cold water 
for the purpose of removing all the soluble salts (sulphocyanide 
of iron and ammonium and the ammonia salts). The insoluble 
residue was intimately mixed with hydrated lime in the propor- 
tion of 30 kg. of lime per cubic meter or 1600 kg. of washed mate- 
rials. Water was added and the whole stirred. After standing 
several hours, the mixture was again lixiviated with cold water. 

The residues obtained from these washings are exposed to the 
air for 3 or 4 months and again treated with water. The wash- 
waters contain ferrocyanides in the fprm of lime salt. The first 
washings, which are more concentrated, are treated with potassium 
carbonate, there being formed insoluble carbonate of lime, whereas 
the potassium ferrocyanide remains in solution. This latter is 
decanted, concentrated, and crystallized. The final washings, 
which are too dilute to be thus profitably treated, are treated with 
a solution of iron protosulphate; a white precipitate of ferrocyanide 
of iron is formed, which on standing in the air becomes converted 
into Prussian blue. 

In his works at Aubervilliers, Gauthier-Bouchard succeeded, by 
this process, in extracting 22,500 kg. of Prussian blue from the 
1500 cu.m. of spent oxid furnished him by the Parisian gas company, 
or an average of 15 kg. per cubic meter. The potassium ferro- 
cyanide produced by the Gauthier-Bouchard process brought 275 
francs per 100 kg. And yet, while recognizing the advantages of 
this process, most of the investigators of that time preferred the 
ignition of the nitrogenous organic substances, notwithstanding 
the empiricism and the imperfections of this latter process. 

At present the Gauthier-Bouchard process, somewhat modi- 
fied, is in operation in Camille ArnouFs works at St.-Ouen- 
1'Aumone, where it was installed in 1875. 

Moreover, almost all the processes which treat the spent oxids 
with a view to the recovery of the cyanogen compounds are modi- 


fications of the Gauthier-Bouchard process. The improvements 
made in the process refer especially to the treatment with water 
and to the conversion into potassium ferrocyanide. 

The processes at present in use differ very little. They may 
be divided into two groups: 

The first group includes those processes in which the spent oxid 
is previously treated with carbon bisulphide in order to remove 
the sulphur which is present in rather large quantities. 

In the second group the cyanogen compounds are immediately 
extracted. These are the ones which are mostly in use, and they 
will now be studied. Their operation may be divided into three 
principal stages: 

(1) Lixiviation of the materials in order to remove the soluble 
salts (ammoniacal salts and sulphocyanides) and to recover the 
ammonia and the sulphocyanides. 

(2) Conversion of the insoluble ferrocyanides into soluble ferro- 
cyanides (sodium and calcium). 

(3) Conversion of the calcium or sodium ferrocyanide into that 
of potassium. 

(1) LIXIVIATION. As has just been remarked the object of this is 
to remove the soluble salts, which consist especially of ammonium 
sulphate, sulphocyanides of ammonium and iron, and some iron 
sulphate. The lixiviation of the materials takes place in filtering- 
vats arranged generally in series of eight on stands or blocks. These 
vats may be of iron, though ordinarily they are made of wood, and 
are 2 meters square and 0.90 meter high, their capacity being about 
3000 kg. spent oxid. They are fitted up with a false bottom, consist- 
ing of a wooden frame B (Fig. 19) resting on wooden beams. This 
frame is covered with a layer, 10 cm. in depth, of twigs or straw (A) 
and this layer is itself covered with a cotton or jute filtering-cloth D. 
A tap R allows the liquid of the false bottom to flow into a wooden 
or cement trench which communicates by openings, closed with 
plugs, with three cisterns (A, B, C) (Fig. 20). 

The lixiviation is carried on as follows: The purifying mate- 
rials are first shoveled into the vats and water is then allowed to 
flow into vat No. 1 so as to cover the materials to the extent of a 
few millimeters only. This is allowed to stand 12-24 hours, at 
the end of which time the liquor is drawn off into the trench and 


collected in the cistern A, and from there it is pumped into vat 
No. 2, at the same time vat No. 1 is treated with a fresh supply 
of water. The water is again allowed to stand in contact with 
the materials for 24 hours, when the liquid is withdrawn from vat 
No. 2 and collected in cistern B, from which it is pumped into vat 
No. 3. The liquid is also drawn off from vat No. 1 into cistern A, 
from which it is pumped into vat No. 2, and so on. At the end 
of the treatment the strong liquors show 10-14 B. and contain 

FIG. 19. 

about 40 grams of ammonia per liter. The pump transfers the 
liquid from cistern C to an upper reservoir, where it will be taken 
up again and distilled with lime in order to obtain the ammonia. 
This is done in the usual way and with the ordinary apparatus 
used in the recovery of ammonia from the ammoniacal liquors. 
After the distillation, there remains in solution calcium sulpho- 
cyanide, which is later converted into potassium sulphocyanide. 

CYANIDES. This may be carried on in two ways: 

(a) In an apparatus fitted up with a stirrer, similar to that in 
Fig. 21. 

(&) In filtering-vats similar in every respect to those used in the 
lixiviation of the materials. 

The former apparatus, provided with a stirrer, is generally a 





FIG. 21. Apparatus Fitted with a Stirrer for the Conversion of the Insoluble 
Cyanides into the Soluble. 


kettle or boiler made of 10-mm. cast iron, with a capacity of 6000 
liters, and ordinarily receiving 2000-3000 kg. spent oxid. First, the 
dilute lixivium is conducted into the apparatus and then 2000-3000 
kg. of the materials are added. The stirrer is set in motion, the 
whole being heated with steam. The mud-like mass flows into the 
filter-presses in order to separate the solution which contains 20-50 
grams of ferrocyanide, expressed as potassium ferrocyanide, per liter. 

The mass is first pulverized with a specially constructed powder, 
then sifted through a 4-mm. sieve, mixed with lime and soda in 
amounts varying with the composition of the mass (which has been 
previously analyzed) and then treated in the boiler. 

When using the filtering-vats the operation is carried on as follows: 

After having been subjected to the first lixiviation the materials 
are allowed to stand several days in order to drain. They are then 
spread upon asphalt or cement surfaces so as to dry them. The 
drying may be hastened by frequently turning the mass about with 
a shovel, this turning also serving to break the lumps. When the 
mass is dry it is sifted through a 4-mm. sieve, then the sifted 
mass is mixed intimately with powdered slack lime, in amounts 
carefully determined by a previous analysis of the mass. Then the 
filtering-vats, which are arranged as in the first lixiviation, are charged 
with this mixture, and water is added so as to cover the materials 
to the extent of a few millimeters. It is allowed to stand 12 to 
24 hours, and the operation is carried on as in the first lixiviation. 
Generally eight or ten vats are used, and lixiviums are obtained show- 
ing 12-14 B., containing from 120-140 grams of Fe (CN 6 )K 4 + 
3H 2 per liter, whereas with the stirring apparatus the solutions 
contained but 40-50 grams of Fe(CN) 6 K 4 . 

(3) PRECIPITATION OF FERROCYANIDES. The lixiviums obtained 
by using the stirring apparatus contain ferrocyanide of calcium and 
sodium, whereas those which are produced by the filtering-vats 
contain the whole of the ferrocyanide in the form of calcium fer- 
rocyanide, Ca2Fe(CN)6. Both of them likewise contain sulpho- 
cyanide of calcium and ammonium. The object of the following 
treatment is to precipitate the ferrocyanides, and this may be done 
in one of three ways: 

(a) By means of iron salts. 

(6) By means of ammoniacal salts. 


(c) By means of potassium chloride. 

Precipitation by Means of Iron Salts. This consists simply in 
precipitating the ferrocyanides in the form of Prussian blue. If the 
lixiviums contain the calcium ferrocyanide they are treated with 
ferrous or ferric chloride; if, on the other hand, they contain sodium 
ferrocyanide, sulphate of iron is used. 

The solution obtained with the stirring apparatus always contains 
sulphides, and on account of the presence of free ammonia they are 
alkaline. The solutions are acidified in a special vat and are allowed 
to stand in order that the sulphur may separate out; after which the 
clear liquid is decanted and subjected to precipitation with an iron 

On account of being cheaper, the use of the ferrous salts 
(FeCl 2 or FeSOJ is preferred, the precipitate being oxidized in 
air. Precipitation is carried on in wooden or iron vats, the iron 
solution being gradually a$ded, stirring the while, and from time 
to time a sample of the liquors is tested to make sure that the pre- 
cipitation is complete. When this point is reached the whole is 
allowed to stand at least 24 hours, and then the supernatum liquid 
is drawn off. The Prussian blue is subjected to the filter-presses 
and then converted into potassium ferrocyanide by treatment with 
potash or with potassium carbonate. 

Precipitation by Means of Ammoniacal Salts. This process is based 
on the insolubility of the double salt Ca(NH 4 ) 2 Fe(CN) 6 : 

Ca 2 Fe(CN) 6 +2NH 4 C1 =Ca(NH 4 ) 2 Fe(CN) 6 +CaCl. 

Sal ammoniac as such is never used; but instead the operation 
is carried on in such a way that the salt is produced in sufficient 
amount at the time of the precipitation by taking care to obtain 
lixiviums which contain enough ammonia so that it will be necessary 
to neutralize them with hydrochloric acid. It is well for this pur- 
pose to add to the lixiviated materials a small amount of a mix- 
ture of non-lixiviatd materials and lime, which will produce the 
ammonia necessary to the reaction. The operation is carried on 
in a stirring apparatus which is kept constantly in motion, hydro- 
chloric acid being added until the reaction is acid. The whole 
is then heated to 80 when the double salt separates out as a white 


powder with a slight bluish tint. When the precipitation is finished, 
the stirring is stopped and the precipitate allowed to settle. The 
clear liquid is drawn off, the precipitate being subjected to the 
filter-press. As the double salt is not entirely insoluble in water 
(there remaining 3.75 grams per liter at 25) it is well to precipitate 
the mother liquors in the form of Prussian blue by means of an 
iron salt. 

The double salt Ca(NH 4 ) 2 Fe(CN) 6 may be treated: 

(1) With lime, in a stirring apparatus, so as to produce pure 
calcium f errocy anide, 

Ca(NH 4 ) 2 Fe(CN) 6 +CaO =Ca 2 Fe(CN) 6 +2NH 3 +H 2 0, 
which may then be converted into potassium ferrocyanide by pre- 
cipitating a double salt CaK 2 Fe(CN) 6 by means of potassium 
chloride, and then converting this double salt into potassium fer- 
rocyanide by boiling with potassium carbonate: 

CaK 2 Fe(CN) 6 + C0 3 K 2 = KJFeCCN) 6 + CaC0 3 . 

(2) With potassium carbonate in the presence of lime: 
Ca(NH 4 ) 2 Fe(CN) 6 +2C0 3 K 2 + CaO 

=K 4 Fe(CN) 6 +2CaC0 3 +2NH 3 +H 2 0. 

In this way solutions of potassium ferrocyanide are obtained 
which are concentrated to 30 B. and then allowed to crystallize. 

Precipitation by Means of Potassium Chloride. This reaction 
gives rise to the formation of a slightly soluble double salt, 
CaK 2 Fe(CN) 6 : 

Ca 2 Fe(CN) 6 +2KC1 =CaK 2 Fe(CN) 6 +CaCl 2 . 

The precipitation may be done either directly in the calcium 
ferrocyanide solutions containing at least 100 grams of K^Fe^N) e, 
or in the same solutions after concentration to 20-25 B. The 
'Operation is carried on at 80 in a small kettle or boiler provided 
with a stirrer. An excess of potassium chloride, added in the form 
of crystals, should be used. The double salt CaK 2 Fe(CN)e is pre- 
cipitated as a light-yellow powder, which may be separated by 
decantation or filtration, and then washed with water, and finally 
treated with potassium carbonate so as to obtain ferrocyanide of 
potassium according to the reaction 

CaK 2 Fe(CN) 6 +C0 3 K 2 =C0 3 Ca +K 4 Fe(CN) 6 . 


waters of the first lixiviation in the form of calcium sulphocyanide. 
They may be extracted by treating the residual solutions from the 
ammonia distillation by precipitation with a sodium or potassium 
salt, concentration and crystallization. They may also be precipitated 
in the form of copper sulphocyanide, which is then decomposed by 
alkaline sulphide. The same mode of treatment is applicable to other 
residual solutions containing sulphocyanides. 

In other works, sulphur which is always present in these masses 
in amounts varying generally from 30% to 40%, but sometimes 
reaching 60% and more, is first of all extracted. Various means 
may be used in bringing this about : carbon bisulphide, or oil of tar 
may be used. In other works the sulphur is extracted by fusion 
with water under high pressure in close dboilers. Finally, a works 
at Marseilles withdraws the sulphur by means of superheated steam 
obtaining in this way flowers of sulphur. 

But the sulphur which is obtained by these various methods is 
always more or less dark in color due to the tarry substances, which 
prevents its use as a commercial and industrial product. All in 
all, this extraction can but give a small profit, and therefore it is 
but little used. The works which carry on the extraction of sulphur 
prefer subjecting the spent oxides to ignition in layer-kilns, according 
to the Maletra system for the extraction of cyanide compounds. 
The sulphurous acid thus formed is utilized in the production of sul- 
phuric acid. There is one objection to this, which is that the sul- 
phurous acid is mixed with carbonic acid produced by the car- 
bonization of the tar products, and, on the other hand, a part of the 
sulphurous acid is continued with the lime which is always in excess 
in the exhausted and treated materials. 

Moreover, various methods have been proposed for the extraction 
of cyanogen compounds from purifying materials, but very few of 
them have been tried on an industrial scale; they will, however, be 
passed in review. 

Valentin's Process. Valentin (English patent No. 3908, Nov. 12, 
1874) recommended treating the materials with water in order to 
remove the soluble salts, and then to treat the residues of this wash- 
ing with carbonate of lime or magnesia, or a mixture of the two, 
at the boiling-point. There are thus formed ferrocyanides of mag- 


nesium and of calcium, which remain in solution, and which may 
then be precipitated in the form of Prussian blue. 

Harcourt's Process. Harcourt (1875) first treats the materials 
with sulphuric acid, the sulphates of iron andjimmonium dissolving, 
whereas the sulphur and the Prussian blue remain insoluble. The 
Prussian blue is separated by means of ammonia and reprecipitated 
from the solution with an iron salt. Harcourt converts the sulpho- 
cyanides into ammonium sulphate by means of sulphuric acid and 
manganese dioxid. 

Kunheim's Process. Kunheim and Zimmermann (German patent 
No. 26884, July 6, 1883) remove the sulphur and the soluble substances 
from the materials, which are then pulverized, sifted, and mixed 
with lime, and treated as follows: The mixture is heated in a closed 
vessel at a temperature between 40 and 100; the ammonia, united 
to the ferrocyanogen, distills and is collected. The solution of 
calcium ferrocyanide obtained is treated in the usual way in order 
to convert it into Prussian blue, or else evaporated and treated with 
potassium chloride in order to form a double cyanide CaK2Fe(CN)6, 
which may then be converted into potassium ferrocyanide by means 
of potassium carbonate. The materials, mixed with lime, may 
also be treated directly with water, thus obtaining an ammoniacal 
solution of calcium ferrocyanide, which on careful treatment under 
definite conditions, in the warmth, yields a precipitate of ferro- 
cyanide of calcium and ammonium difficultly soluble in water. 
When this precipitate is treated in a closed ves*sel with lime it 
yields pure calcium ferrocyanide, while the ammonia distills off. 
The calcium ferrocyanide is then converted into Prussian blue, or 
into yellow prussiate by the ordinary methods. 

HempePs Process. The process of Hempel and Steinberg 
(German patent No. 33936, Nov. 21, 1884) consists in first extracting 
the masses with water at 60 C., and then treating them at the 
ordinary temperature with a 10% ammonia solution in quantities 
four or five times more than sufficient to convert them into ammo- 
nium ferrocyanide, which latter is then converted into Prussian blue 
or yellow prussiate. 

Wolfram's Process. In this process (German patent No. 40215, 
Nov. 14, 1886) the masses are first treated with dilute sulphuric or 
hydrochloric acid. The acid solution thus obtained is neutralized 


with oxid of iron. The ammonium sulphocyanide is thus decom- 
posed, as is likewise the ammonium f errocyanide ; sulphate of ammo- 
nium is formed, whereas Berlin blue, sulphur, and hydroferrocyanic 
acid are precipitated. Sulphur is extracted by means of carbon 
bisulphide in suitable apparatus. 

Donath's Process. Donath and Ornstein's process (German 
patent No. 110097, May 29, 1898) is based on the characteristic which 
Berlin blue possesses of dissolving in concentrated hydrochloric acid, 
and being reprecipitated when the solution is evaporated or when 
it is allowed to stand in air. The materials are first treated with 
very dilute acid so as to dissolve the oxid of iron. The residue is 
dried, and treated with concentrated hydrochloric acid, the Berlin 
blue dissolving and imparting to the solution a light-yellow 
color. It is precipitated from this solution by the addition of 
water, the precipitate appearing in the form of small crystalline 

Richter's Process. Richter (French patent No. 196144, 1889) 
begins by heating the materials in closed vessels by means of a stream 
of water- vapor. The ammonia which is set free is collected in sul- 
phuric acid. The residue is likewise treated in a closed vessel with 
hydrochloric acid so as to obtain iron perchloride. The residue from 
this treatment is then mixed with magnesium carbonate and treated 
with water in order to extract the magnesium ferrocyanide which 
may be converted by the ordinary methods. 

Esop's Process. Esop recommends (Ztseh. fur angewandte 
Chemie 1889) digesting the masses with water and then subjecting 
them to the filter-press, the residue being treated with lime and 
sodium sulphate, a mixture which it seems gives better results than 
lime alone. 

Marasse's Process. Marasse of Berlin converts the whole of the 
ferrocyanide of the purifying materials into sulphocyanides (French 
patent No. 158731, Nov. 22, 1883) . After having treated the materials 
with water they are heated in a closed vessel at a temperature above 
l60 C. and in the presence of an excess of lime, the amount of lime 
being determined according to the quantity of ferrocyanides in the 
materials to be treated. At first there is formed calcium ferrocyanide 
and calcium sulphide, which latter acts upon the ferrocyanide forming 
calcium sulphocyanide: 


Ca 2 Fe(CN) 6 +3CaS 2 =3Ca(CNS) 2 +FeS 2 . 

According to Marasse the decomposition is complete (?) . The solution 
of calcium sulphocyanide is purified and converted into ferrocyanide 
by means of finely divided iron. The lime may be replaced by 
potassa or soda. 

Holbling's Process. Holbling (Ztsch. fur angew. Chemie 1897) 
proposes a similar method, which consists in the conversion of the 
Prussian blue contained in the purifying materials into barium 
sulphocyanide by simply heating the materials during several hours 
in the presence of a slight excess of barium sulphide (5%), or only 
one-half hour with a large excess (10 to 15%), and under a pressure of 
three atmospheres. Holbling claims that the conversion is complete. 
It is filtered and tjie solution of barium sulphocyanide obtained is 
treated by a current of sulphurous acid, or better carbonic acid, in 
order to decompose the excess of barium sulphide and to convert it 
into barium thiosulphate and sulphur, or into barium carbonate 
respectively, which being insoluble are separated by filtration. 

Lewis' Process. The following process is recommended by 
Lewis: After having removed the sulphur from the purifying mate- 
rials they are boiled with milk of lime. The solution thus obtained, 
containing ferrocyanide and sulphocyanide of calcium, is treated 
with sulphurous acid, and a solution of ferrous-ferric sulphate which 
causes the formation of Prussian blue. This is filtered, and from 
the residual solution the sulphocyanides are removed by means of a 
copper salt, as in the treatment of the ammoniacal liquors. 

Masco w's Process. The last process concerning the treatment 
of purifying materials in order to remove from them the cyanogen 
compounds to be mentioned is that very original one of Mascow 
(French patent No. 301916, 1901). Mascow makes use of the char- 
acteristic which ammonia possesses of dissolving the alkali cyanides. 
Toward this end he converts the cyanogen compounds into alkali 
cyanides soluble in ammonia, whereas the other impurities are 
converted into products insoluble in that reagent. The materials 
are dried and then mixed with any one of the following substances: 
Sodium, magnesium, aluminium, iron, zinc, or their oxids, or car- 
bonates mixed with charcoal, or with calcium carbide, or even with 
both these substances. Either one or the other of these substances is 


used, depending upon the composition of the materials. Thus, if 
the materials are rich in sulphocyanides, metallic iron should be 
added to the charcoal or to the potassium carbonate used. The 
mixture is then heated out of contact of air, or in the presence of 
an inert gas, at such a temperature that the whole of the cyanogen 
is converted into alkali cyanide, which may then be dissolved in 
.ammonia, the impurities remaining insoluble. 


POTASSIUM ferricyanide (K 6 Fe2(CN)i 2 ), or red prussiate of potash 
as it is more generally known in the arts and in commerce, J of suffi- 
cient importance industrially to require some mention relating to 
its preparation. 

It is always obtained by the oxidation of potassium ferrocyanide. 

The Chlorine Process. The oldest process, and one still in use, 
consists in causing chlorine-gas to act on potassium ferrocyanide, 
the reaction being as follows : 

2Fe(N) 6 K 4 + 2C1 = 2KC1 + K 6 Fe 2 (CN) 12 . 

This treatment may be carried on either in the moist or the 
dry way, but the latter method is very rarely used, the moist method 
being preferred. The operation is quite difficult to conduct, since 
it requires great care and attention. Practically it is carried on 
as follows: 

A solution of potassium ferrocyanide indicating 26 B. is made 
in a copper boiler placed on a grate. This solution is transferred 
to a wooden vat, provided with a movable cover, into which a cur- 
rent of , chlorine is conducted until the addition of a ferric salt 
no longer produces a precipitate in the liquor. 

The saturation point is of extreme importance, for if too much 
chlorine be used there is formed a green precipitate of complex 
composition, to which the name of Berlin green has been given, 
and which prevents the ferricyanide from crystallizing, and besides, 
notwithstanding its insolubility, is extremely difficult to separate 
as it passes through the niters. On the other hand, if too little 
chlorine be used the ferricyanide obtained contains non-decom- 
posed ferrocyanide. 



Frequent tests are made by adding a ferric salt to a portion 
of the liquor, and when a precipitate is no longer produced, just 
at that point must the further addition of chlorine be stopped. In 
order to tell exactly the saturation point, the color of the solution 
should be examined by candle light, the end of the reaction being 
indicated by the fact that the solution being at first greenish becomes 
red. But this change in color, although quite distinct in dilute 
solution, is scarcely perceptible in concentrated solution. The 
testing should preferably be done with a ferric salt absolutely free 
from ferrous salts. 

Stirring must be kept up continually during the addition of chlo- 
rine, otherwise the ferricyanide formed at certain points would be 
broken up under the prolonged action of chlorine, which would pro- 
duce the above-mentioned green compound. 

When the addition of chlorine is stopped, the solution is filtered 
and immediately transferred to a copper boiler similar to that in 
which the ferrocyanide was dissolved, and concentrated to 27-28 B. 
by continued boiling, for the crystals have a tendency to become 
deposited on the sides of the vat. When this point is reached the 
liquor is transferred to wooden vats or crystallizing vessels, where 
it is allowed to stand for five days. At the end of this tune the 
mother-liquors are separated from the red prussiate crystals by 
decantation. These mother-liquors are subjected either to two 
further concentrations, to 28 to 29 B., or else they may be used 
in dissolving a fresh quantity of yellow prussiate which is to be 
subjected to the action of chlorine. When the conversion is com- 
plete the solution of ferricyanide is concentrated to 29 B. and left 
to crystallize. These new mother-liquors which are decanted are 
concentrated until they register 31 B. while hot; after which they 
are transferred into vats where the potassium chloride is precipitated. 
After standing six or seven hours, the liquors while still warm are 
decanted, and may again be used to dissolve ferrocyanide. The 
crude crystals of the four operations are then collected and dissolved 
in hot water in a copper boiler; the solution is concentrated to 27 
B. while hot, and then transferred into wooden vats or crystallizing 
vessels, where they are left for several days. 

As large crystals are commercially much more important, in order 
to obtain a beautiful crystallization, it is advisable to pour gently on 


the surface of the solution about 20 litres of water, which floating on 
the surface prevents the formation of small crystals. When the 
crystallization is complete the mother-liquors are decanted, and 
may be used in dissolving a fresh quantity of crude crystals. They 
may thus be used five or six times provided they are not too heavily 
charged with potassium chloride. When this salt becomes too 
abundant the mother-liquors are concentrated in order to remove 
it by crystallization, and it is then sold as fertilizer. 

The crystals of potassium ferricyanide are allowed to drain and 
then are dried upon flat iron plates gently warmed with waste heat. 
This treatment should preferably be conducted in a dark place, and 
be done as rapidly as possible in order to avoid too long contact with 

In this way for 100 parts of yellow prussiate about 70 parts of 
ferricyanide are obtained, the theoretical yield being 77.9. 

The process by the dry way consists in causing chlorine to act upon 
powdered ferrocyanide, placed in very thin layers in revolving 
apparatus or in chambers similar to those used in the manufacture of 
chloride of lime. 

The ferrocyanide is first deprived of part of its water of crys- 
tallization in order that it may be powdered, as chlorine exerts 
but a slight action on the anhydrous salt; then it is ground with a 
grindstone, sifted, and subjected to the action of chlorine till ab- 
sorption no longer takes place. The reaction is exactly the same 
as in the moist way: Ferricyanide and potassium chloride are 
formed which may be separated by crystallization. Quite often 
the product obtained in the dry way is sold just as it is when 
removed from the absorption apparatus, i.e., in the form of a 
powder consisting of a mixture of ferricyanide and chloride of 
potassium. Various other methods have been devised for the pro- 
duction of red prussiate. 

Reichardt's Process. Reichardt (1869) proposed replacing chlo- 
rine by bromine, while Kramer recommended digesting Prussian blue 
with potassium hypochlorite. Rodgers advised precipitating a 
solution of a mixture of 2 parts potassium sulphate and 1 part iron 
alum with barium cyanide, then to filter, concentrate, and crystallize. 
It is not known that these methods have been tried on an industrial 


The action of ozone or of ozonized oxygen has likewise been 
tried, the ferrocyanide being very rapidly converted into ferri- 

Electricity produces the same result. Two methods have been 
invented with a view to utilizing the electric current on ferrocyanide. 
These are the processes of the Societe des Mines at Bouxvillers, and 
of Dubosc. 

It is well known that under the action of the electric current 
passing through an aqueous solution of ferrocyanide, the latter is 
converted into ferricyanide which appears at the positive pole, 
while at the negative pole potassium is deposited, which, in contact 
with water, forms hydrogen and potassa, 

2Fe(CN) 6 K 4 =Fe 2 (CN) i 2 K 6 + K 2 , 

but it is likewise known that the action is reversible, the electric 
current converting ferricyanide into ferrocyanide. This phenomenon 
is explained by supposing that in the first case the ferricyanide is 
reduced by the hydrogen produced at the negative pole, while in the 
second case, the oxygen of the. positive pole oxidizes the ferro- 
cyanide. On the other hand, the prolonged action of the potassa 
converts a part of the ferricyanide into ferrocyanide. 

Process of the Mines at Bouxvillers. This process (French patent 
No. 176675, Oct. 15, 1886) aims at avoiding these very objections. 
The conditions under which the electric current should be conducted 
have been so carefully studied that there is no formation of Prussian 
blue, and the ferricyanide formed is not decomposed. The electrodes 
,are placed in cells separated by porous diaphragms, the negative 
cell containing water, the positive cell being filled with a solution of 
potassium ferrocyanide. 

If under these conditions an electric current of an electromotive 
force of 1.4 to 5.4 volts be conducted the ferrocyanide is converted 
into ferricyanide which is formed in the positive cell, whereas in the 
negative cell caustic potash is formed with the liberation of hydrogen. 
In this way the two solutions are separate, and the potash does not 
exert its injurious action on the ferricyanide, and thus a pure solution 
of ferricyanide is obtained, and it remains only to concentrate and 
to crystallize it. 


The water of the negative cell may be replaced by mercury, in 
which case an amalgam of mercury and potassium is formed. 

Dubosc's Process. Dubosc (French patent No. 207193, July, 24, 
1890) likewise uses the electric current in order to convert the ferro- 
cyanide into the ferricyanide. The electrolysis takes place in the 
presence of sodium chloride. At the same time, or afterwards, a 
current of carbonic acid is passed through, which neutralizes the 
alkaline base and separates the ferricyanide formed from the car- 
bonate and the chloride: 

2K 4 Fe(CN) 6 + 2 + 2C0 2 = 2C0 3 K 2 + K 6 Fe 2 (CN) 12 . 

The Process of the Deutsche Gold und Silber Scheide-Anstalt 

(French patent No. 218246, 1891) has for its object the avoiding 
of the, formation of soluble salts, which remaining in the solution 
together with the ferricyanide contaminate the latter, which often 
requires purification more or or less costly. 

It consists in using an alkaline-earth ferrocyanide, which after 
oxidation only leaves an insoluble compound. The oxidation is 
made more easily, it seems, and either the electric current or per- 
manganate or any other oxidizing agent which does not leave behind 
any soluble compound may be used. In any case, the small amount 
of alkaline-earth base which dissolves may be precipitated either 
by sulphuric or carbonic acid. 

Calcium ferrocyanide is preferred, in which case, when perman- 
ganate is used as the oxidizing agent, the reaction is as follows: 

3Ca 2 Fe(CN) 6 + 7K 4 Fe(CN) 6 +2KMn0 4 

= 10K 3 Fe(CN) 6 +2MnO +6Ca(X 

The oxid of manganese and the greater part of the lime, being 
insoluble, remain in suspension. By passing a current of carbonic 
acid, the small amount of dissolved lime is easily precipitated. After 
filtration an absolutely pure solution of ferricyanide is obtained,, 
which may be concentrated and crystallized. 

The process may likewise be applied to the chlorine method, 
the oxidation being more rapid and the yield greater than by the 
ordinary method. But this oxidizing agent leaving behind soluble 
compounds, pure solutions are not obtained, as is the case where 
the oxidizing agent leaves behind only insoluble impurities which 
may be easily fierlted off. 


Kassner's Process. This process (1893) is based on a reaction 
which was pointed out by Lunge in 1881. This investigator recom- 
mends the oxidation of ferrocyanide by means of lead peroxid 
and carbonic acid according to the reaction 

2FeK 4 (CN) 6 + + H 2 = Fe 2 K 6 (CN) 12 + 2KOH. 

Kassner, however, no longer uses peroxid of lead, but instead 
an alkaline-earth plumbate, e.g. calcium plumbate. This sub- 
stance, the formula of which is Ca 2 Pb0 4 or, better, CaO,Pb0 2; pos- 
sesses the peculiar property when in contact with even the weak- 
est acids, such as carbonic acid and even carbonates and some other 
salts, of becoming converted into lead bioxid and the calcium 
salt of the acid used. Thus if calcium plumbate be heated with 
sodium carbonate at 130 under pressure, an insoluble mixture of 
chalk and lead bioxid is obtained, caustic soda being in solution: 

Ca 2 Pb0 4 + 2C0 3 Na 2 + 2H 2 = Pb0 2 + 2C0 3 Ca + 4NaOH. 

Now then, if a mixture of chalk and lead bioxid be held in sus- 
pension in a solution of potassium ferrocyanide and a current of 
carbonic acid be conducted through it, there will be formed potassium 
ferricyanide, lead oxid, carbonates of lime and of potash, accord- 
ing to the reaction 

2FeK 4 (CN) 6 +Pb0 2 +2C0 3 Ca +C0 2 

= Fe 2 K 6 (CN)i 2 +PbO + 2C0 3 Ca +C0 3 K 2 . 

By adding to the solution calcium ferricyanide, the carbonate of 
potash is converted into carbonate of lime, so that nothing remains 
in solution except potassium ferricyanide, which may be separated 
by filtration, concentration, and crystallization: 

3Fe 2 (CN)i2K 6 +3C0 3 K 2 +Fe 2 (CN) 12 Ca3=4Fe 2 (CN) 12 K 6 +3C0 3 Ca. 

It is best to add the calcium ferricyanide after the oxidation 
with the lead salt, for the chalk formed in this second reaction may 
thus be collected, and so not hinder the recovery of the lead salt. 

Calcium ferricyanide is obtained by the action of calcium plum- 
bate on the corresponding ferrocyanide. A very intimate mixture of 


lead peroxid and chalk is thus made, and with a slight excess of 
this oxidizing mixture calcium f errocyanide in concentrated solution, 
under pressure, is oxidized. The solution of calcium ferricyanide 
obtained may be directly utilized in the conversion of alkali car- 

Carl Beck's Processes. These processes (German patent No. 15459, 
Nov. 28, 1893; No. 16088, May 4, 1894; No. 17677, May 22, 1895) 
are based on the action of persulphates, which are very energetic 
oxidizing agents, as is well known. The reaction is as follows: 

Either the persulphate of ammonia or that of sodium may be 
used, but on account of the greater solubility of the former, it -is 
preferred. A solution of potassium ferrocyanide is prepared by 
dissolving this salt in exactly its weight of hot water. When this 
solution has cooled to 60, a solution of ammonium persulphate 
containing 540 grams of this salt per liter of water is slowly added. 
The reaction being very lively, heat is liberated to such an extent 
as to necessitate cooling the vessel in which the reaction is con- 
ducted. The neutral double sulphate of ammonium and potash, 
being but slightly soluble, is deposited on cooling. It is separated 
by decantation; the ferricyanide is then crystallized. On account 
of the relatively high cost of persulphates it seems improbable that 
this process should be used on a large scale. 

Williamson's Process. One process which has been somewhat 
.spoken about lately and which had already been pointed out by 
Williamson, still remains to be mentioned. It consists in starting 
with the product known as soluble Prussian blue, a product which 
is obtained by pricipitating iron sesquioxid with an excess of potas- 
sium ferrocyanide. The precipitate obtained is washed, the wash- 
water rapidly becoming blue, due to the presence of the compound 
[Fe(CN) 6 ]2Fe2K 2 , or ferric potassium ferrocyanide. When this prod- 
uct is treated with potassium ferrocyanide, it yields potassium ferri- 
cyanide and ferrous potassic ferrocyanide, 

[Fe(CN) 6 ]2Fe 2 K 2 +2K 4 Fe(CN) 6 =Fe 2 K(CN)i2+2Fe 6 (CN) 6 FeK 2 . 

ferric potassic ferro- ferrous potassic 

cyanide. ferrocyanide 


It is only necessary to digest the potassium ferrocyanide with a 
slight excess of potassium ferri-ferrocyanide, then to filter, evaporate, 
and allow to crystallize. The ferricyanidethus obtained is perfectly 
pure, and, as may be seen, the process requires neither great care 
nor complicated apparatus. There remains on the filter a mixture 
of potassium ferro-ferrocyanide and the excess of potassium ferri- 
ferrocyanide used. This latter product may be recovered and may 
again be used in the manufacture of a fresh amount of ferricyanide 
by treating it with nitric acid. The same amount of this product 
could thus be used indefinitely. 

Notwithstanding its extreme simplicity we do not know if this 
process has been used industrially. 


SULPHOCYANIDES, sulphocyanates, or rhodanates as they are some- 
times called, are very little used in the arts. Yet, at one time they 
were very important industrially, for they were considered a very 
profitable source of manufacture as an intermediary product of 
cyanides. - On this account their production was the basis of several 
processes about which the investigator and manufacturer should 
know. These processes, especially two of them, mark a real progress 
in the cyanide industry, and they will be minutely described as they 

Before entering upon the study of the various methods for the 
manufacture of sulphocyanides, it will be well to briefly recall 
the different methods of obtaining these compounds. 

Sulphocyanides may be produced: 

(1) By the direct action of sulphur on a cyanide, 


or on a f errocyanide, either by boiling or by ignition. 

(2) By igniting nitrogenous substances with potassium sulphate, 
or with sulphur and potassium carbonate. 

(3) By the action of cyanogen, hydrocyanic acid, or cyanides on 
metallic sulphides, 

2CN + K 2 S = CNK + CNSK, 

or by the action of hydrocyanic acid on a mixture of ammonia, 
sulphur, and ammonium sulphide. 

(4) By the action of carbon bisulphide on ammonia on heating: 

CS 2 +4NH 3 = (NH 4 ) 2 S +CNS(NH 4 ). 



(5) By the action of heat, or of alkalis on thiosulphocarbamates: 

CS \SK 2 + 2KOH 

(6) By the 'action of heat on ammonium thiocarbamate (Berthelot, 
Bull, de la Soc. chim. de Paris, 1868) : 

CO \SNH 2 4 +heat =H2 +CNS(NH 4 ). 

(7) By the decomposition of fulminates by the aid of hydrogen 

(C 2 N 2 2 )2Hg 2 +4H 2 S =2HgS +2C0 2 +2CNS(NH 4 ). 

(8) By the action of water and heat on Thio-urea: 

CS(NH 2 ) 2 =CNS(NH 4 ). 

(9) By the action of hot sulphuric acid on nitrogenous organic 

Of all these methods of preparation there is one which should be 
especially retained in mind, for it forms the basis of the methods of 
production of sulphocyanides on an industrial scale. That is the 
one which depends on the action of carbon bisulphide on ammonia. 

Gelis' Process. To Gelis, a Frenchman, belongs the honor of 
having applied this reaction to an industrial process. 

This process is already old (1860), and it was put in operation for 
the first time in the inventor's own works at Villeneuve-la-Garenne. 

It was carried on as follows, the operation comprising two distinct 

(1) The action of sulphide of carbon on ammonium sulphide, 
with formation of ammonium sulphocarbonate : 

CS 2 +2(NH 4 HS) =CS 3 (NH 4 ) 2 + H 2 S. 

(2) Conversion of ammonium sulphocarbonate into ammonium 
.sulphocyanide by heating it to 100 with potassium sulphide 

2CS 3 (NH 4 ) 2 + K 2 S = 2CNSK + 2NH 4 HS + 3H 2 S. 


The first stage takes place in an apparatus fitted up with a wide- 
bladed stirrer. The sulphocarbonate formed is transferred to a 
sheet-iron still together with potassium sulphide and the mixture 
is heated to 100. The hydrogen sulphide and the ammonium 
sulphydrate set free are condensed in a sheet-iron cylinder entirely 
surrounded with water, into which gaseous ammonia produced in 
another boiler is conducted, which is used in absorbing the hydrogen 
sulphide in order to form ammonium sulphydrate, which, together 
with that produced in the decomposition of ammonium sulpho- 
carbonate, is used in the manufacture. The condensation ends in 
a coil in sheet-iron boxes fixed up with compartments, and finally 
in bottles. 

The sulphocyanide was then treated at 140-160 with reduced 
iron in deep wide pans made of cast iron and hermetically sealed. 

In his report to the Imperial Commission of the Exposition at 
London in 1862, Gelis mentions the fact that his experiments have 
been carried on with more than 1000 kg. at one time, and that the 
raw materials are products easily found in the market. He adds that 
the manufacture is extremely easy 

In the " Annales des Mines du Conservatoire des Arts et Metiers, " 
1862, page 55, Payen gives the net cost of ferrocyanide manufactured 
by Gelis' process, the cost being based on the production of 30,000 kg. 
potassium ferrocyanide. 

Carbon bisulphide (crude) 35,000 kg. @ 45 fcs. per 100 kg 15,750 fcs. 

Potassium sulphate 36,400 " " 40 " " " 14,510 " 

Ammonium sulphate 25,300" " 35 " " " 8,875" 

Reduced iron 50,000 "" 10 " " " 5,000" 

Quicklime 17,500"" 4" " " 700" 

Cost of converting the potassium sulphate into potassium sulphide, 3 fcs. 

per 100 kg. . 1,092 " 

Labor, 12 men @ 3.50 fcs. per day, 30 days 1,260 " 

Fuel 600 " 

Hent and general expenses for one month 1,000 ' ' 

Losses of raw materials, etc., 15% of expenses 7,322 ' ' 

56,139 fcs. 
Deducting from the above one third of the potash in the 

form of carbonate 5,000 fcs. 

25,000 kg. sulphur @ 13 fcs 3,250 " 

8,250 fcs. 

Net cost for 30,000 kg. potassium ferrocyanide 47,889 fcs. 

or 1.59 fcs. per kilogram. 


GehV process had but a short existence, as to-day it is entirely 
abandoned, because it is, in fact, rather difficult to operate it on a 
large scale. Besides, it should be remarked that only half of the am- 
monium sulphocarbonate is converted into potassium sulphocyanide 
at the time of the action of potassium sulphide, and, moreover, it 
requires costly and complicated apparatus. 

Gelis 7 method was again taken up about 1878 by two manufac- 
turers, A. de Gunzburg and Tcherniac (French patents of Feb. 12, 
1878, April 25, 1879, Dec. 24, 1880), who improved it remarkably. 
The process is as follows : 

(1) Production of thiosulphocarbamate of ammonia by the direct 
union of carbon bisulphide and ammonia at 100 under pressure: 

CS 2 + 2NH 3 = NH 2 CS SNH 4 . 

(2) Conversion of this salt into ammonium sulphocyanate by 
heating at 105: 

NH 2 CS SH 4 N = NCS NH 4 + H 2 S. 

(3) The conversion of ammonium sulphocyanate into calcium 
sulphocyanate by distillation with quicklime, and the reproduction 
of half of the ammonia used in the reaction : 

2NCS NH 4 + Ca(OH) 2 = (NCS) 2 Ca + 2NH 3 + H 2 0. 

(4) The conversion of calcium sulphocyanate into potassium 
sulphocyanate by treating it with potassium sulphate : 

(NSC) 2 Ca + S0 4 K 2 = S0 4 Ca + 2CNSK. 

(5) Conversion of the potassium sulphocyanide into potassium 
ferrocyanide with iron at 450 according to the reactions which we 
have already pointed out : 

CNSK + Fe = FeS + CNK , 
FeS + 6CNK * Fe(CN) 6 K 4 + K 2 S. 


(The object of Tcherniac's process was the -production of potassium 

As may be seen, the whole of these reactions forms a really com- 
plicated work, and difficult enough to carry on an industrial scale, 
although theoretically it appears quite simple. And it is only by 
reason of unheard-of efforts, of rare perseverance, and of long and 
patient investigations, which are all to the honor of Tcherniac and 
de Giinzburg, that these two learned manufacturers succeeded in 
exploiting their process on a large scale. 

The Campagnie Generate des Cyanures, which is exploiting the 
patents of Tcherniac and de Giinzburg, operates in the following 
way in its works at St. Denis, the complete manufacture comprising 
five operations: 

(1) Preparation of ammonium thiosulphocarbamate. 

(2) Preparation of ammonium sulphocyanate. 

(3) Preparation of calcium sulphocyanate. 

(4) Preparation of potassium sulphocyanate. 

(5) Preparation of potassium ferrocyanide. 

(1) Preparation of Ammonium Thiosulphocarbonates. As has been 
seen, this product, results from the action of carbon bisulphide on 
ammonia. The operation is carried on in a series of small auto- 
claves, forged iron boilers, tested to a very high pressure, and her- 
metically covered. 

Each one of these autoclaves is provided with a thermometer, a 
manometer, a wide-bladed stirrer, and three tubulatures or cocks, 
one for the inlet of the solutions, the other for the exit of the gases 
which are produced, and the third for emptying the apparatus. 
They are encased in an exterior wrapper heated with steam. The 
reaction is conducted separately in each one of the autoclaves repre- 
sented in Fig. 22. A pump p feeds the autoclaves with a mixture 
of carbon bisulphide, 20% ammonia, and ammoniacal liquors fur- 
nished by preceding operations. 

When the apparatus has been suitably charged with this mixture 
the cock connecting with the pump is closed, and the stirrer is set 
in motion. Steam is admitted through the tube, V, and the whole 
heated till the thermometer registers 100. At this moment the 
inlet of steam is stopped, and the stirrer is kept going till the pressure 
in the autoclave is 15 atmospheres; the operation may then be. 


considered finished. The product of the reaction is a mixture of 
ammonium sulphocarbonate, and carbon bisulphide in excess. The 
cock of the compressing tube, C, plunging to the bottom of the 
apparatus is opened, and owing to the effects of the high pressure 
in the autoclave, the mixture is violently driven into the still, A, 

FIG. 22. 

represented in Fig. 23, and in which the conversion of ammonium 
sulphocyanate takes place. 

(2) Separation of Ammonium Sulphocyanate. The still in which 
this precipitation is carried on consists of an ordinary boiler, heated 
to a temperature of 105-110 C. by means of a coil of steam 
placed at the bottom. Under these conditions the thiosulphocar- 
bonate is decomposed in ammonium sulphocyanate and hydrogen 



sulphide, while the remaining carbon bisulphide and ammonia distill. 
The still is surmounted with a cylindrical vessel, B } called an en- 
trainment device, the object of which is to separate the gaseous 
products from the liquid products mechanically drawn over during 
the distillation. These latter come with the gaseous products 
through the tube, &, into the entrainment device, there they are 
condensed and returned to the still, A, through the tube, c, which 
plunges into the liquid to be distilled, while the gaseous products 
continue their course to the absorption apparatus. 

This apparatus consists of two columns filled with pieces of coke, 
placed above a surface heat-exchanger, which is itself built upon a 
very large receiver, into which the products of condensation are col- 

FIG. 23. 

lected. A gasometer bell, whose capacity is about 15 cu. m., is used 
as a regulator, and at the same time holds back the residual gases 
of the condensation, consisting almost entirely of hydrogen sulphide. 
The gases which emerge from the entrainment device and which 
consist of a complicated mixture of hydrogen sulphide, ammonium 
sulphide (obtained from the action of hydrogen sulphide on ammonia 
in excess), water-vapor, and carbon bisulphide, pass into the coke 
column, C, then into the exchanger, E, and are condensed in the 


vessel ; R. A pump, P, takes this liquid and transfers it through the 
tube, /, to the upper part of the coke column, where it is discharged 
in the form of a continuous shower which, while making sure of a 
complete condensation, prevents any stoppage which the deposits 
of ammonium sulphide might occasion. 

The second column, C'-D', is used as a reflux condenser, and 
allows the last portions of the liquid, which might have escaped 
treatment to be collected. 

Carried out in this way, the condensation is very imperfect; in 
fact, notwithstanding all the desirable improvements of the condensa- 
tion apparatus, hydrogen sulphide always carries along an appre- 
ciable amount of carbon bisulphide, sometimes even 20% of the 
product used. Notwithstanding this, the inventors of this process 
have succeeded in preventing completely the disastrous effects of 
this contamination by making the hydrogen sulphide bubble through 
oil, preferably heavy petroleum oil. Under these conditions the 
carbon bisulphide only is absorbed by the oil, and it only requires a 
distillation to separate it and to revivify the oil, whereas the hydrogen 
sulphide escapes in an almost pure state. (Patent of May 31, 1881.) 
Thus carried on, this treatment, which is one of the finest examples 
of continuous operations, gives a large yield which may even reach 
95% of the theoretical. 

The ammonium sulphocyanate remaining in the still is dis- 
charged after the distillation through the cock d. 

These first two operations of Tcherniac and de Giinzburg's process 
require very strong apparatus. With the exception of the coil in 
the still, which is of tin or of aluminum, the apparatus should be 
of forged or of cast iron, which metals are known through experi- 
ence to be the most suitable for this kind of work, in fact, in the 
presence of a slight excess of ammonium sulphydrate, iron is suffi- 
ciently resistent. On the other hand, it is absolutely necessary 
that the coil should be of tin or of aluminum, for in this part of 
the apparatus the iron, no longer protected by the ammonium sul- 
phide, would be attacked by a small quantity of free sulphocyanic 
acid, produced by the partial dissociation of ammonium sulpho- 
cyanide, ferrous sulphocyanate being formed which would con- 
taminate the product and color it red; tin is but slightly attacked, 
and pure aluminum not at all. 


If absolutely pure ammonium sulphocyanide is desired it will 
be necessary to carry on the operation in an aluminum apparatus. 
A still entirely of aluminum has been constructed, and the results 
obtained have been in all points entirely satisfactory. 

At present a great deal of ammonium sulphocyanide is used 
in the preparation of aluminum mordants in dyeing, and the salts 
to be used for this purpose should be especially free from iron. 
In this case the manufacture is carried on in aluminum apparatus, 
and it is stopped at this point; the ammonium sulphocyanide 
which remains in the still is cleared out, evaporated at the tem- 
perature of 125, and then allowed to crystallize in wooden vats 
lined with tin. 

When the operation has been carried on in an iron still and the 
ammonium sulphocyanide thus obtained therefore contains ferrous 
sulphocyanide, which, in contact with atmospheric oxygen, is con- 
verted into ferric sulphocyanate and gives the characteristic red 
color of this latter salt, it is necessary, if it is desired to obtain a 
white salt capable of remaining white, to precipitate the ferrous 
salt with ammonium sulphydrate or simply to subject the solu- 
tion, to which a little ammonia has been added, to the action of 
a current of air, which precipitates the whole of the iron as peroxide. 
This is allowed to stand and then filtered and the solution evapo- 
rated in a tin boiler. 

If, on the other hand, the object is to manufacture potassium 
ferrocyanide the operations which have been previously described 
are continued. 

(3) Preparation of Calcium Sulphocyanate. This is based on' 
the following reaction: 

2CNS NH 4 + CaO = (CNS) 2 Ca^+ 2NH 3 + H 2 0. 

The apparatus which is used for this treatment consists of a 
vertical boiler; or still (Fig. 24) heated by means of the steam coil, V. 
This coil surrounds a perforated sheet-iron basket in which lime 
is placed. Besides, this still or reservoir is provided with a ther- 
mometer and a diverter similar to that of the still just described. 
The lime having been placed in the basket the reservoir is charged 
with the solution of ammonium sulphocyanide, and the tempera- 
ture raised to 125. Under these conditions the reaction indi- 


cated above is brought about and the ammonia set free is dis- 
tilled. When no more ammonia distils over the reaction is con- 
sidered finished, calcium sulphocyanate remaining in the reservoir. 
The ammonia distilled over is condensed in the following apparatus: 
On emerging from the still the ammonia passes into the diverter, 
whose object it is to separate the liquids from the vapors ; a separa- 
tion which is rather delicate, owing to the abundant froth produced 
by the solution of calcium sulphocyanate, but which is easily enough 
done in the entrainment device where the foam liquefies and flows 
back into the reservoir, whereas the ammonia continues its course 
reaching the exchanger, C, where it is partly condensed. The last 

FIG. 24. 

portions are held back in the absorber, D, cooled by a coil contain- 
ing cold water. The amount of water which flows is so regulated 
that a 20% solution of ammonia is obtained, which may be used 
in the manufacture of ammonium thiosulphocarbonate. 

The solution of calcium sulphocyanate which remains in the 
distill ing-reservoir is removed through the cock, C, and then treated 
so as to convert it into potassium sulphocyanide. 

Conversion of Ammonium Sulphocyanate into Potassium Sulpho- 
cyanate. This operation takes place in open cylindrical boilers 
heated directly by fire and fitted up with scraper-stirrers. First, 
a concentrated and boiling solution of potassium sulphate is prepared 


in the boilers, so that the amount of this salt is somewhat greater 
than that, which is exactly necessary for the conversion of the am- 
monium sulphocyanate. Then the calcium sulphocyanide is run in 
in small portions at a time, the stirrers being set in motion after each 
addition. Calcium sulphate is precipitated. The resulting mash 
is subjected to filter-presses in order to separate the calcium sulphate. 

As the filtrate still contains some calcium sulphocyanate, unde- 
composed, the latter is precipitated with potassium carbonate, and 
after filtration the filtrate is evaporated at 125 and crystallized. 
Besides sulphocyanide of potash, this solution contains some sulphate, 
chloride and carbonate of potash, which latter salts crystallize first. 
These crystals are removed and the remaining solution is evaporated 
to dryness, this solution containing only potassium sulphocyanide. 
The residue is fused at 300 in deep, wide pans, made of cast iron, and 
thus yields a product as pure as possible. 

It now only remains to convert the sulphocyanide into potassium 
ferrocyanide. Although the study of this preparation does not 
exactly belong to the scope of this chapter, and has already been 
discussed in a preceding chapter, a few words will be said, because of 
the fact that Tcherniac and de Giinzburg's process has especially to 
do with the production of potassium ferrocyanide. 

These investigators carry out this conversion as follows: The 
potassium sulphocyanide, as above obtained, is pulverized and inti- 
mately mixed with powdered reduced iron, or sifted cast-iron powder 
The mixture is quickly introduced into metallic boxes with covers, A 
(Fig. 25), which are placed in a sulphur stove kept at a temperature 
of about 450, the stove being heated directly over the fire. When 
the operation is finished the boxes are removed and placed in another 
stove hermetically sealed and surrounded with cold water, where 
they are thus cooled out of contact with air. The fused and cooled 
mass, consisting of a mixture of iron sulphide and potassium cyanide, 
according to the reaction 


is treated with water, and yields a solution of potassium ferrocyanide 
containing 30-35% of this salt, which it is only necessary to purify 
by evaporation and crystallization. 


This last part of Tcherniac and de Giinzburg's process was for. 
a long time the cause of the failure of the method. It was not until 
much feeling about and numerous investigations that these inventors 
succeeded in evolving the following conditions which assure the 
success for the method: 

FIG. 25. 

(1) The sulphocyanate should be perfectly dry and pure. 

(2) The iron should be free from rust and impurities. 

(3) The mixture should be as intimate as possible. 

(4) The temperature of fusion should be 450; no higher than 
500, no lower than 300. 

(5) The fusion and the cooling should take place out of contact 
with air. 

If all these conditions are not strictly followed the results may 
be defective. 


Such is the process of Tcherniac and de Giinzburg; it occupies 
an important place in the history of the cyanide industry, and has 
given results truly remarkable; it is one of the few processes that 
has lived. Other manufacturers have been animated by the works 
and the process of Tcherniac and de Giinzburg, which they have to 
some extent improved. 

Deiss and Monnier's Process. Thus it is that the Deiss and 
Monnier Company of Saint-Denis (Patent No. 217,825, Dec. 3, 
1891; March 2, 1892) recommend preparing sulphocyanides by the 
action not of an aqueous solution of ammonia, but of gaseous am- 
monia on carbon bisulphide. According to these inventors, the 
reaction is more rapid, and larger amounts of raw materials may 
be treated in small and less complicated apparatus than that of 
Tcherniac's process. Moreover, the reaction takes place in the 
cold and at a normal pressure, which therefore requires less costty 
apparatus. The process is otherwise carried on as follows: The 
sulphide is mixed with rich carbides (petroleum, vegetable or mineral 
oils, higher alcohols, e.g., butyl or amyl, etc.), to the extent of 30 
to 50%. By means of a pump this mixture is brought in contact 
with ammonium sulphide, the object of which is to dissolve the 
thiosulphocarbonate as fast as it is formed, the mixture being kept 
cold by means of running cold water. Ammonium thiosulpho- 
carbonate is immediately formed. When the whole of the carbon 
bisulphide is combined, the solution of thiosulphocarbonate, sepa- 
rated from the carbide by decantation, is run into an apparatus 
which is heated externally by a coil of steam, where this salt is 
decomposed into ammonia and hydrogen sulphide, which are set 
free, and into ammonium sulphocyanide, which remains in the still. 
This latter solution is concentrated and allowed to crystallize. The 
hydrogen sulphide set free in this reaction is conducted into a washer 
containing ,oil, where it leaves behind the carbon bisulphide, which 
was entrained. Some ammonium sulphydrate is likewise formed 
by the action of the gaseous ammonia on hydrogen sulphide, and 
this is collected in a receiver containing water. 

The reaction pointed out by Millon and Gelis successively, 

CS 2 +4NH 3 =CNS -NH 4 + (NH^aS, 
converts only half of the ammonia used in the reaction into cyanogen. 


compounds; the other half, to a large extent at least, being converted 
into ammonium sulphide and ammonium sulphydrate. Now, then, the 
ammonium sulphide causes an enormous pressure inside the apparatus, 
which necessitates special appliances very costly and complicated. 

Means of overcoming the serious objection of the formation of 
ammonium sulphide have therefore been sought. All the improve- 
ments to Gelis's reaction toward this end depend upon the same 
principle: The absorption of the hydrogen sulphide by a non- volatile 
base, which diminishes the pressure appreciably; since, for example, 
the pressure of calcium sulphydrate at the boiling-point is not 
greater than that of water, whereas that of ammonium sulphide is 
about seven times greater (A. E. Wareing). Moreover, the ammonia 
is thus rendered free for the conversion into sulphocyanide. 

Hood and Salomon's Process. One of the first improvements 
along this line is that of Hood and Gordon Salamon. (English 
patent No. 5534, 1891, and German patent No. 12018, Feb. 27, 1892; 
Aug. 3, 1893). It consists in treating while hot, a mixture of carbon 
bisulphide and ammonia, in the presence of a mixture of lime and 
an oxidizing agent, such as manganese peroxide. ("For this pur- 
pose Wei don mud well washed in order to completely remove the 
calcium chloride may be taken"), or ferric oxid, etc. 

The operation is conducted in a boiler autoclave, into which the 
mixture of lime and oxid of manganese is introduced, after which 
the apparatus is heated to 100, when the carbon bisulphide and 
ammonia, mixed in molecular proportions, are added a little at a 
time. When the reaction is finished the product is tahen up with 
water which dissolves the calcium and manganese sulphocyanates, 
leaving an insoluble residue of manganese sulphide and sulphur. 
These latter are separated by filtration; from the residue the man- 
ganese dioxide is revivified and again used. The filtered solution is 
treated with an alkali carbonate in order to precipitate the lime and 
manganese and to convert their sulphocyanates into alkali sulpho- 
cyanate. This precipitation is fractionated, the manganese having 
a greater affinity for the carbonic acid than the lime has; and so 
manganese carbonates separates out first. 

Brock's Process. Somewhat similar is the process of J. Brock, 
A. E. Hetherington, P. Hurter, J. Raschen (English patent No. 21451, 
Nov. 1893; Dec. 1894). In the course of their researches on this 


important question these chemists noticed that the presence of 
manganese and iron oxides was superfluous, and that the lime alone 
sufficed. Their process consists, therefore, in heating in a cylin- 
drical apparatus, made of cast iron or steel and placed horizontally, 
a mixture of carbon bisulphide, ammonia, and lime in the following 
proportions : 

Carbon bisulphide 100 parts 

Slaked lime 200 ". 

Ammoniacal solution containing. 45 "! 

dry .ammonia-gas, together with a sufficient amount of water to 
make the mass fluid. 

The amount of ammonia used is twice that required by the 

2CS 2 + 2NH 3 + 2Ca(OH) a = Ca(CNS) 2 + CaS 2 H 2 + 4H 2 0. 

The cylinder has double walls, steam circulating between the 
walls, bringing the temperature of the interior and its contents to 
100 C. The cylinder is provided with a mechanical stirrer, which 
allows the mass to be continually stirred during the reaction, lasting 
from 2 to 6 hours. The same bottom through which the stirrer 
passes is provided also with a safety-valve, an outlet tube for draw- 
ing off, and a lid for the charging. A thermometer and a manom- 
eter allow the temperature and pressure to be watched. 

After driving off the excess of ammonia by distillation the whole 
is filtered in order to remove the lime, and carbonic acid is passed 
through the product. Under these conditions the calcium sul- 
phide and the calcium sulphydrate are decomposed, hydrogen sul- 
phide is set free and driven off, and carbonate of lime is precipi- 
tated. After filtering there remains a solution of calcium sulpho- 
cyanide which may be treated by any of the appropriate methods 
for ts conversion into alkali sulphocyanide. 

Process of the British Cyanide Company. This process (German 
patent No. 14611, April 16, 1894; Jan. 10, 1895) consists, likewise, in 
causing ammonia to act on carbon bisulphide in the presence of a 
base, such as lime, without the use of any oxidizing agent. The 
apparatus used, a double-walled autoclave cylinder provided with 
a stirrer, differs but little from that of the preceding process. It 


is first charged with 17-18.5 parts of an ammoniacal solution con- 
taining 7.15% dry gas, 101-102 parts hydrated lime, finely powdered, 
containing 72-75% CaO. 

These two substances are intimately mixed and then are added 
76 parts carbon bisulphide; the autoclave is closed and heated 
gently, the stirrer being kept in motion, when the manometer indi- 
cates 2 atmospheres pressure the heating is discontinued; the pres- 
sure continues to rise up to 6 atmospheres, when it falls. 

At this point the heat is again applied till the temperature of 
115-120 is reached, and v this is maintained for several hours. 

As in the preceding process, the product of the reaction is treated 
with carbonic acid which displaced hydrogen sulphide from the 
calcium sulphide and the calcium sulphydrate. The carbonate of lime 
is separated by filtration, the filtrate which contains only sulphocyan- 
ide being treated with an alkali salt which thus yields alkali sulpho- 
cyanide on evaporation and crystallization. The first part of the 
evaporation takes place in a distilling apparatus in the presence of 
caustic soda, and at boiling temperature in order to recover the small 
amount of ammonia remaining in solution (about 5%). The hydro- 
gen sulphide set free may either be burned in order to yield sul- 
phurous acid to be used in feeding the lead chambers, or else treated 
in the ordinary way for the extraction of sulphur from it. Conroy, 
who has made a whole series of investigations on these processes, 
clears up this subject considerably in an interesting paper in The 
Journal of the Society of Chemical Industry (1896). From the in- 
vestigations conducted by this English savant, in collaboration 
with Zahortki, it follows that: 

(1) An excess of ammonia is absolutely indispensable to carry 
on the reaction properly, as it is well known that in this reaction 
thiocarbonate of lime is also formed, 

3CS 3 + 2Ca(OH) 2 = 2CaS 3 C + 2H 2 + C0 2 , 
which in contact with water gives 

CaCS 3 +3H 2 0= 3H 2 S+CaC0 3 , 

unless there is an excess of ammonia, and in this case the reaction 

2CaCS 3 + 2NH 3 = (CNS) 2 Ca + 3H 2 S + CaS. 


(2) The addition of lime does not exert any influence on the 
yield of sulphocyanate; it serves only to diminish the pressure. 

(3) Carbon bisulphide and calcium sulphide unites in order to 
form soluble calcium sulphocarbonate, and this union is best made 
at the temperature of 50-60. 

(4) The solution of calcium thiocarbonate may be converted 
quantitatively into sulphocyanate; but in order to obtain a favor- 
able yield it is necessary to work under pressure and in the presence 
of a large excess of ammonia. 

Albright's Process. A later improvement along this line, is that 
brought about by G. S. T. Albright, at Birmingham (German patent 
No. 4324, May 4, 1895; October 21, 1895). It consists practically in 
making use of magnesia instead of lime. Under pressure, magne- 
sium hydrate fixes hydrogen sulphide, which is set free by the action 
of carbon bisulphide on ammonia in order to form magnesium 
sulphydrate; and this salt again liberates hydrogen sulphide on 
boiling, while at the same time magnesium hydrate is reproduced 
and may be used for the next operation: 

+ 2H 2 S=MgH 2 S 2 +2H 2 0; 
MgH 2 S 2 +2H 2 = Mg(OH) 2 +2H 2 S. 

The operation is carried on in a boiler provided with a stirrer 
where magnesium sulphocyanide is at the same time produced. It 
is well to add to the magnesia a sufficient quantity of lime to fix 
completely the sulphocyanic acid formed. The insoluble magne- 
sium hydrate is separated by filtration from the calcium sulpho- 
cyanide, which latter is then converted into alkali sulphocyanide 
by double decomposition with an alkali sulphate or carbonate. 

Tcherniac's Process. Another class of methods for the pro- 
duction of sulphocyanides makes use of nitrites, carbon bisulphide, 
and hydrogen sulphide. Such are the processes of Tcherniac, 
Goerlich and Wichmann. This process had already in 1856 been 
pointed out by Schlagdenhaufen, who had observed that by heating 
carbon bisulphide and a nitrite in a closed tube there were formed 
sulphocyanate, carbonic acid, and hydrogen sulphide, but that 
under these conditions a large portion of the carbon bisulphide 
burns with the formation of sulphuric and carbonic acids, and at the- 


same time a large part of the nitrogen was lost as free nitrogen or in 
the form of nitrogen protoxide. If, on the contrary, as is done in 
Tcherniac's process, a mixture of carbon bisulphide, nitrite, and 
hydrogen sulphide be heated in an autoclave an almost quantitative 
yield of sulphocyanide is obtained. 

Tcherniac's process consists (French patent No. 248163, June 14, 
1895; Oct. 16, 1895) in heating the following mixture in an auto- 
cla,ve provided with a mechanical stirrer: 

Nitrate of the base usea 1 molecule 

Carbon bisulphide 1 

Hydrogen sulphide 2 molecules 

The hydrogen sulphide may first be made to act on the nitrite, or 
<else be compressed into the autoclave, which is heated to 150 C. 
until the manometer indicates a depression, which shows the end of 
the reaction. This may be expressed thus: 

RN0 2 +CS 2 +2H 2 S =CNRS +S 3 +2H 2 0. 

In order to make use of the whole of the nitrite the hydrogen 
sulphide should be in slight excess. The sulphur separates from the 
aqueous solution of the sulphocyanide, in the form of a crystalline 
crust, very easy to remove, and the sulphocyanide obtained is almost 
pure, and may be used for any purpose in the arts. 

Goerlich and Wichmann's Process. This process (German patent 
No. 9831, June 7, 1895; July 30, 1896) is identical in every respect 
with that of Tcherniac's. 

Finally, it only remains to mention Goldberg and Siepermann's 
process (German patent No. 9494, Jan. 14, 1895; June 13, 1895). It 
consists in heating under pressure a mixture of carbon bisulphide, 
ammonia, and alkali- or alkaline-earth sulphite or bisulphite. The 
reaction which already begins at 100, goes on actively at 120 
to 130 by stirring constantly, and especially if the operation is 
carried on in the presence of an alkaline-earth sulphite. 

In a general way the reactions may be expressed by the following 
equations in the case of an alkaline base : 


2CS 2 + 2NH 3 + R 2 S0 3 =2CNRS + 3S + 3H 2 0, 
2CS 2 + 2NH 3 + R 2 S 2 3 =2CNRS + 4S + 3H 2 0, 

or in the case of an alkaline-earth base (lime, magnesia), 

2CS 2 +2NH 3 +RS0 3 = (CNS) 2 R+3S+3H 2 0, 
2CS 2 + 2NH 3 + RS 2 3 = (CNS) 2 R + 4S + 3H 2 0. 

The sulphur thus formed is collected as fast as it is formed under 
the solution of sulphocyanide in the form of a fused mass. 




PRUSSIAN blue, or ferric ferrocyanide, was, as we have already 
mentioned, the first cyanogen compound known. Its discovery 
occupies a very important place in the history of chemical industry, 
for it is in consequence of this happy finding that all the cyanogen 
compounds were produced. 

The discovery of Prussian blue dates back to the year 1710, and 
like that of many chemical products it was due purely to chance. 
A Berlin manufacturer of colors, named Diesbach, wishing to precipi- 
tate cochineal lake by means of potash, and not having any of this 
substance on hand borrowed some of a pharmacist of that city, 
Dippel by name. This pharmacist gave him some potassium car- 
bonate which he had used in rectifying an empyreumatical oil, of 
animal origin, of the same name. When Diesbach made use of this 
product, instead of the red lake which he wished to prepare, he 
obtained a magnificent blue precipitate. Surprised at this extraor- 
dinary phenomenon he took Dippel into his confidence, who was 
not slow in suspecting that this precipitate was due to the action 
of potash on iron alum, which Diesbach had used. In fact, on 
repeating the experiment Dippel obtained an absolutely similar 
result. From that time he resolved to make something out of this 
remarkable discovery. In a paper which he presented to the Acad- 
emy of Berlin in 1710 he calls attention to this body, without 
however disclosing the mode of preparation, and he joined with 
Diesbach in the manufacture of this new product. The method 
of manufacture was kept secret till 1724, at which time an English 
chemist, Woodward, member of the Royal Society of London, suc- 
ceeded in reproducing Prussian blue, and made public the method 



of preparation. This publication created a great sensation at the 
time, for with the exception of indigo no other blue coloring-matter 
was known. Woodward's method, practically unchanged, is the one 
carried on to-day in the works where Prussian blue is prepared. 

It was begun by preparing a " blood-lye" obtained by treating 
with hot water the product of ignition of dried blood or other organic 
materials in the presence of potassium carbonate. This lye was 
then exposed to air in shallow pans until a lead salt gave no longer 
a precipitate, and then treated with a mixed solution of alum and 
copperas. The whole was constantly stirred with a stick, a bri^/ 
effervescence taking place, while at the same time a greenish precipi- 
tate was formed. It was allowed to stand for some time, and then de- 
canted, the precipitate being washed with water until it had acquired 
a blue color. It was then drained, compressed in the form of cubes 
which were allowed to dry in the open air by means of gentle heat. 

Prussian blue is also formed when ferrocyanide of potassium or 
barium or ferrohydrocyanic acid is precipitated by means of a salt 
of iron peroxide, or when potassium cyanide is precipitated by a 
ferro-ferric salt: 

18KCN + 3FeCl 2 + 2Fe 2 Cl 6 = 18KC1 + Fe 7 (CN) 18 . 

It is formed by the action of hydrocyanic acid on ferro-f erric- 
hydrate, or of a ferric salt on ferrous cyanide, 

9Fe (CN) 2 + 2Fe 2 Cl 6 = Fe 7 (CN) 18 + 6FeCl 2 , 

or by the action of an oxidizing agent, such as chlorine- water on 
ferrous cyanide, hydroferrocyanic acid, ferro-potassic-cyanide. 

The best method of obtaining a splendid quality of Prussian blue 
is to precipitate potassium ferrocyanide with an acid solution of 
sulphate of iron protoxide (ferrous sulphate, green vitriol, copperas). 
This is done in the following manner : 

Potassium ferrocyanide and ferrous sulphate are separately 
dissolved in 15 times heir weight of water, or else a solution of 
each is prepared by dissolving 6 parts of the salt in 15 parts water. 
The solutions are then mixed, and while constantly stirring, a 
mixture of 1 part concentrated sulphuric acid and 24 parts fum- 
ing hydrochloric acid is added. 


A grayish-white precipitate of ferro-potassic-ferrocyanide is 
formed, the mother-liquors containing potassium sulphate which 
may be removed by evaporation. The precipitate is allowed to 
stand several hours, and then it is washed with a large amount of 
water. It remains only to make it blue, i.e., to oxidize it. Under 
the influence of atmospheric oxygen or of any oxidizing agent, the 
ferro-potassic-ferrocyanide is, in fact, converted into Prussian blue: 

+ 3 =Fe7(CN)i8+3FeK 4 (CN) 6 +re 2 3 . 

As may be supposed, many methods have been used in the oxida- 
tion of ferro-potassic-ferrocyanide. 

First, air was used. This is the oldest method, and the one 
which gives the poorest results. 

Solutions of clarified hypochlorite of lime have likewise been 
much used, this solution being added in small quantities at a time. 
But although this process has been used a long time it has the 
objection of forming calcium sulphate, which is only slightly soluble 
together with the Prussian blue, which former, in mixing with the 
Prussian blue, weakens the color just so much, or at least forms 
white spots in the blue which depreciates the value. 

In his " Traite de Chimie appliquee aux Arts industriels " Girardin 
gives a formula for making Prussian blue by means of hypochlorite 
of lime. The work is carried on as in the preceding, by precipi- 
tating copperas with prussiate in the following proportions: 

Crystallized ferrocyanide ................... 10 parts 

Copperas ................................. 11 

The precipitate formed is treated with hypochlorite of lime: 
Chloride of lime dissolved in 100 parts of water ......... 1.5 parts 

and then with weak hydrochloric acid: 

Hydrochloric acid diluted with 100 parts of water ......... 5.0 parts 

Aqua regia at ordinary temperature and chromic acid have 
also been used, both of which methods have been abandoned, the 
first being too costly and the latter being objectionable on account 
of its leaving chrome alum, which is of little use, in the mother- 
liquors. In the latter case, the treatment was carried on as fol- 


lows : A solution of 10 kg. of bichromate of potash in 100 liters of 
hot water was made; after cooling, 135 kg. of sulphuric acid (com.) 
was added, and this mixture was gradually poured on the white 
precipitate potassic ferro-ferrocyanide, which was diluted with boil- 
ing water until the precipitate had acquired a beautiful intense- 
blue color. 

A boiling solution of potassium chlorate may profitably be used, 
but the best procedure is that which consists in using a warm solu- 
tion of iron perchloride or of ferric sulphate. When this solution 
acts on the white precipitate, it is brought back to the state of proto- 
salt, which may then be treated with ferrocyanide and be used 

Whether the oxidation of ferro-potassic-ferrocyanide be carried 
on by one or other of the above methods, the conversion into Prus- 
sian blue is never complete, for another part of the white precipi- 
tate produces a compound which is also blue, and which seems 
to be a ferri-potassic-ferricyanide. 

Although the preparation of Prussian blue seems at first sight 
very simple, it nevertheless requires care if a pure product of beau- 
tiful shade is to be obtained. The essential conditions which apply 
to all the methods just described are the following: 

(1) The iron solution should always be poured into the potas- 
sium ferrocyanide and never the reverse, if it be not desired that 
the precipitate formed should enclose a large quantity of potas- 
sium ferrocyanide. (2) It is well to digest the Prussian blue with 
hydrochloric or nitric acid in order to remove the iron oxid com- 
pletely, which always reduces more or less the intensity of the color. 

The iron salt used should be as pure as possible, and especially 
should not contain copper, since the salts of this metal with ferro- 
cyanide give a reddish precipitate which injures the brilliancy of the 

In the preparation of ordinary commercial Prussian blues, alum 
in various amounts is very often added at the moment of the pre- 
cipitation. The alum salt forms aluminum ferrocyanide, which has 
the gelatinous appearance of aluminium, it being intimately mixed 
and held in the Prussian-blue precipitate, increasing the weight 
without appreciably injuring the tint, unless too great amounts 
are used. 


The alum is added in various amounts according to the quality 
of Prussian blue desired. For pure blues, not any is added. 

For a fine quantity of blue, one part of alum is used for three or 
four parts of ferrous sulphate; for an ordinary blue, one part to two 
or three of iron sulphate; and for blues of inferior quality, equal 
parts of the two salts. In certain blues of very low quality, as much 
as three parts of alum are used for one of ferrous sulphate. 

Moreover, the varieties of Prussian blue are very numerous, and 
the quality of this product depends altogether on its mode of prepara- 
tion. There are fifteen or twenty classes of Prussian blue, all differ- 
ing from one another in their composition and color. The principal 
ones are: Berlin blue, Prussian blue of Paris or Milori blue, Paris 
blue, fine and dark, ordinary deep blue, and mineral or Antwerp 
blue, to which oxid of zinc or magnesium carbonate is often 

Soluble Prussian blue. This compound, whose exact composition 
is not yet known, and which according to some is a union of or- 
dinary Prussian blue and potassium ferrocyanide, and according to 
others a ferricyanide of iron and of potassium, is formed when a 
salt of iron peroxid (iron perchloride) is precipitated by potassium 
ferrocyanide in excess. The precipitate thus formed is a very 
beautiful blue insoluble in the solution containing potassium ferro- 
cyanide, but soluble in pure water. 

It is likewise obtained when a solution of iron iodide containing 
an excess of iodine is poured into a concentrated solution of potas- 
sium ferrocyanide (Reade). The blue precipitate thus formed is 
entirely soluble in water, even after drying. 

Turnbull's blue. TurnbulPs blue is really a ferrous ferricyanide, 
Fe 5 (CN)i 2 . Its tint is still a more beautiful blue than that of 
Prussian blue. It is obtained by gradually pouring a hot solution 
of potassium ferricyanide, free from ferrocyanide, into a solution 
of a ferrous salt. This should be allowed to stand some time in 
the presence of an iron salt, if it be desired to obtain a product 
free from potash. It may be distinguished from ordinary Prussian 
blue by treating it with a hot potash solution, when it yields a 
precipitate of ferro-ferric hydrate and yellow prussiate, whereas 
Prussian blue gives ferric hydrate. 

Monthiers' blue, or ammoniacal Prussian blue. This compound, 


which is more stable than ordinary Prussian blue, is a ferric iron and 
ferric ammonium ferrocyanide, its formula being 

Monthiers obtained it as follows: An ammonia solution is poured 
into a pure solution of iron protochloride, the precipitate is rapidly 
filtered, taking all precautions to avoid contact with air, and the 
filtrate is gradually poured into a solution of potassium ferrocyanide. 
A white precipitate which becomes blue on contact with air and also 
a precipitate of ferric hydrate are formed. By treating with ammo- 
nium tartrate for several hours at 60-80, the ferric hydrate may 
be removed, the ammoniacal Prussian blue being insoluble. This 
is washed with water. 

Antimony blue. This is nothing more than a Prussian blue of a 
beautiful shade, obtained in a special way, and falsely called anti- 
mony blue, as it contains no trace of this metal. It is obtained 
by boiling with potassium ferrocyanide the white precipitate formed 
when a tartar emetic solution is treated with concentrated hydro- 
chloric acid; the blue precipitate formed is repeatedly treated with 
hydrochloric acid in order to remove the antimony completely. 
The antimony salt seems, therefore, to play no part except to facili- 
tate the formation of this compound. 


FORMERLY the cyanide industry owed its importance to the use 
of Prussian blue and of potassium ferrocyanide. Potassium cyanide 
had but limited application in medicine, in photography, in labora- 
tories (as a reagent), and in the art of gilding and electrotyping. The 
chemical industry was therefore interested in the production of the 
first two compounds. To-day the reverse is true, Prussian blue 
finds but limited uses, 50% of the potassium ferrocyanide products 
being converted into potassium cyanide, and of all the cyanogen 
compounds the latter is the one most in use. 

It has already been mentioned that the chief application of this 
salt is in the extraction of gold from its minerals, and it is due to 
this one use, which has become of considerable importance, that the 
industry of cyanogen and its compounds owes its present develop- 

Although the question of the treatment of gold minerals belongs 
rather to a metallurgical treatise, we must, however, mention the 
subject on account of its importance and the close bonds which unite 
it with the cyanide industry. 

In fact, the methods for the extraction of gold by means of potas- 
sium cyanide have been considerably extended, and are destined 
still to increase and to become universal. The results thus far obtained 
are most satisfactory as well from an economical standpoint as from 
the standpoint of the yield, and there is no doubt as to the future. 

The idea, which is the basis of these processes, is old. The solu- 
bility of gold in potassium cyanide has long been known. Faraday 



observed this fact, later Prince Bagration did the same. But to 
Eisner belongs the honor of being the first to study the conditions 
under which the solution takes place. This investigation showed 
that oxygen was essential : 

2Au + 4KCN + + H 2 = 2K Au(CN) 2 + 2KOH. 

This theory was vigorously combatted by MacArthur and Forest^ 
who were the first to think of applying this reaction to the extraction 
of gold on an industrial scale ; but to-day it is an accepted fact that 
the solution of gold in potassium cyanide cannot take place without 
the help of oxygen, and is facilitated by the presence of any oxidiz- 
ing agent (peroxides of sodium, barium, lead, manganese, perman- 
ganate, bichromate, nitrates, chlorate, potassium ferricyanide). 

Furthermore, Christy (Jr. Soc. Chem. Ind., 1898, p. 332) has 
shown that the presence of free cyanogen and potassium cyanide is 
absolutely indispensable, the former being used in the formation of 
gold cyanide, which with the latter forms a soluble double cyanide. 

As may be seen, the amounts of oxygen and of cyanide of potas- 
sium essential to the solubility of gold are very small. If the above 
equation be considered 

(2 Au + 4KCY + + H 2 = 2KAuCy 2 + 2KOH) 

it will be noticed that 130.4 parts of potassium cyanide by weight 
dissolve 196.8 parts of gold, i.e., approximately 2 parts of cyanide 
to 3 parts of gold. As to the oxygen, only 15.96 parts are required 
to dissolve 396.6 parts of gold, i.e., 1 part oxygen to 25 parts precious 
metal. This oxygen is furnished in more than sufficient quantity 
by the amount of air occluded in the minerals and by the oxygen 
dissolved in the water used in the preparation of cyanide solutions. 

In practice, the amount of cyanide used is always somewhat 
larger than that required theoretically, because the losses which occur 
during the "cyaniding" must be taken into account. The causes 
of these losses have been carefully studied by Ch. Butters, Clennell, 
and Mosenthal (Engineering and Mining Journal, Oct. 1892), and 
may be thus set forth : 

(1) The oxidation of the auriferous minerals, the result of which 
is the precipitation of a part of the potassium cyanide in the 


form of Prussian blue. The auriferous minerals now being worked 
in South Africa almost always contain iron pyrites, which lat- 
ter, under the double action of air and of atmospheric moisture 
become oxidized, thus converting the mineral into the form of " free 
milling/' as it is called in the 'Rand, with formation of iron sulphate 
and free sulphuric acid: 

FeS 2 + H 2 + 70 = S0 4 Fe + S0 4 H 2 . 

As the oxidation continues there are formed insoluble basic 
sulphate and insoluble ferric sulphate: 

10S0 4 Fe +50 =2(Fe 2 3 )2S03 +3[Fe 2 (S0 4 ) 3 ]. 

Wilstein Berzelius 

If, therefore, a mineral of this kind partially oxidized be placed 
in the presence of a cyanide solution the ferrous sulphate slowly 
acts on the potassium cyanide, forming cyanide of iron and potas- 
sium sulphate: 

S0 4 Fe +2CKN =Fe(CN) 2 +S04K 2 . 

But in the presence of a large excess of potassium cyanide, the 
iron cyanide becomes in its turn converted into potassium ferro- 
cyanide, which, in contact with ferric salts, yields Prussian blue: 

Fe(CN) 2 + 4KCN=FeK 4 (CN) 6 , 
3FeK 4 (CN) 6 +6S0 4 Fe +30 =Fe 2 3 + 6S0 4 K 2 +Fe 7 (CN)i 8 . 

This conversion may be appreciably avoided by adding caustic soda 
or lime in order to saturate the free acid, but nevertheless there is 
always a partial conversion of cyanide into ferrocyanide. 

(2) The action of the oxygen of the air on cyanide solutions. 
As is well known, the cyanides are very oxidizabie salts, the action 
of air converting them, first into cyanate and then into carbonate: 

+ 0=KCNO, 
2KCNO + 3 = C0 3 K 2 + C0 2 + N 2 . 


(3) The action of carbonic acid of the air on the cyanide solu- 
tions : 

2KCN+C0 2 + H 2 0=C0 3 K 2 +2CNH. 

(4) The action of metals other than gold existing in the min- 
erals. The cyanide exerts its action on these metals, among which 
are most frequently met: copper, arsenic, zinc, nickel, cobalt. 

A. W. Warwick has studied the solubility of gold in potassium 
cyanide, and from an article published in the Engineering and 
Mining Journal, June 29, 1895, the following conclusions are drawn. 

(1) The presence of oxygen is an important factor for the solu- 
bility of gold in potassium cyanide. 

(2) The solubility increases with the temperature. This fact 
explains why better results are obtained in warm countries than 
in those where the climate is subject to temperature variations. 

(3) For a given time strong solutions are more active thart 
dilute ones. 

(4) Zinc exerts a prejudicial action. It becomes precipitated 
on the gold and causes the action of the cyanide gradually to cease. 

(5) Copper likewise exerts a decomposing action, but much 

(6) The presence of gold chloride much increases the solubility, 
whereas potassium chloride exerts no action, 

2AuCl 2 + 6KCN = 2K Au(CN) 2 + 4KC1 + 2CNC1, 

which means that the chloride, bromide, and iodide of cyanogen 
exert a favorable action on the dissolving power of potassium 
cyanide. But, according to the author, this action is only indirect, 
and the role of the halogen elements consists only in setting free 
the oxygen necessary for the solution of gold in the cyanide: 

8KCN+Au 4 +2H 2 0+0 2 =4KCN-AuCN+4KOH, 
4KCN AuCN + 2CNBr +4KOH=2KCN AuBr +4KCN +2H 2 +0 2 . 

This formation of gold-bromine-cyanide of potassium is quite, 
probable. (Lindbom has, in fact, obtained this compound.) 


(7) The gold-silver alloys dissolve less easily in potassium cyanide, 
than does pure gold. 

(8) Gold dissolves less easily in ferrocyanide and sulphocyanide 
of potassium than in the cyanide. 

Having given these preliminary principles let us pass to the 
work of the extraction of gold by the said cyanide processes. To 
McArthur and Forest belongs the honor of having had the idea 
of utilizing the dissolving power of cyanide of potassium. Their 
process consisted in treating a mineral with a dilute solution of 
cyanide, then to precipitate the gold out of this solution by means 
of strips of zinc. As will be seen this process has been much improved, 
either by its authors or by other investigators. The treatment 
of gold minerals comprises two essential parts : 

(1) Solution of the gold in the cyanide. 

(2) Precipitation of the gold from these solutions. 

Solution. The cyaniding processes are especially used in the 
Transvaal in the Wittwatersrand, or Rand district as it -is most 
generally called. It is known that the gold in the Transvaal min- 
erals occurs in a very finely divided condition, which makes amalga- 
mation very difficult; it is quite different, however, with the process 
of cyaniding, which may be carried on all the more easily the more 
finely divided the gold occurs. 

As the mineral is brought out of the mines it is subjected to the 
first sorting, this being done on an inclined plane, the object being 
to remove most of the quartz and foreign matters. A second picking, 
by hand, by means of a current of water removes the gangue. It is 
then crushed, ground, and amalgamated. These two operations 
are carried on simultaneously in mills containing mercury. The 
jamalgam thus formed is filtered under pressure, then distilled in 
retorts, the mercury being driven over while the gold remains behind. 
The non-amalgamated portion or pulp containing an appreciable 
amount of gold is treated with a current of water; then it passes over 
porous -copper amalgamating plates where a fresh quantity of gold is 
deposited. The pulp is then concentrated, yielding what is called 
concentrates. In this operation two classes of residues are obtained : 
The heavy residue, called tailings, the lighter, called slimes. The 
tailings and the slimes are important residues, reaching 60-70% 


of the mineral at the Rand; the former contains 7-10 grams of gold 
per ton, the latter 4-7 grams. 

It is especially these residues which are treated with potassium 
cyanide in order to extract the gold left from the amalgamation. 
However, the mineral may thus be treated directly. 

Before touching upon the treatment either of the mineral, the 
tailings, slimes, or concentrate, the following four points should be 
carefully brought out by analyses concerning these substances: 

(1) The gold-content, so as to know the amount of potassium 
cyanide to be used. 

(2) Whether the mineral or the tailings contains the gold in a 
finely divided state, or in large grains; this will indicate the length 
of treatment with the cyanide solution. 

(3) Whether the mineral on the tailings be acid or neutral. 

(4) Whether the mineral or the tailings contain an appreciable 
quantity of metals other than gold and silver, having some affinity 
for cyanogen. 

The auriferous materials will be treated according as they have 
one or other of the above characteristics. These points having been 
clearly established the treatment of minerals or tailings may be 
undertaken. The tailings are transferred to large lixiviating vats, 
sometimes made of wood or brick or cement, and sometimes of 
mortar, and rectangular or cylindrical in form, whose dimensions 
vary according to the works. 

At the works of the African Gold Recovery Company where 
the processes of McArthur and Forest are exploited, the vats are 
wood, cylindrical in shape, 13 meters in diameter and 2.4 meters 
deep, with a capacity of 350 tons of mineral. 

The Langlaate Estale Company and the Block Brick Company 
use circular vats of brick 12 meters in diameter and 3 meters deep, 
containing 400 tons of mineral. 

At the works of the Crown Reef Company the vats are 
rectangular, of brick and cement, 12 meters long, 11 meters wide, 
3 meters deep. 

The vats of the Durham-Rondepoort Co. and of the Simmer 
and Jack Company are circular, made of wood; the former being 
12 meters in diameter and 2.1 meters deep; the latter 12.6 meters 
in diameter and 4.2 meters in height. 


At Robinson's works smaller circular vats are in use, holding 
only 75 tons of mineral, while at the new Primrose works, the lixivi- 
ating vats are very large and capable of holding more than 400 tons 
of mineral. 

When wooden vats are used it is customary to cover the inte- 
rior with a layer of paraffine or of a coal-tar and asphalt compound, 
experience having shown that the wood retains an appreciable 
amount of gold. 

The filtering-vats, the use of which is becoming general, are 
provided with a false bottom, consisting of a wooden framework 
made of laths covered with a mat of cocoa fibers, or a double mat 
of jute, or a layer of jute and one of coca fiber, and sometimes even 
with quartz fragments. These vats are also provided with a two- 
branched drainage-pipe; one for dilute and the other for concen- 
trated solutions. 

Side gates or sluices are used in discharging the mineral after 
its treatment with cyanide. 

First, the vats are filled with the mineral up to within 4 or 5 cc. 
of the top, the contents carefully leveled and the cyanide solution 
run in. This solution is generally prepared by dissolving the cyanide 
in a small amount of water in a small wooden vat, and then dilu- 
ting this solution to the required strength. 

When acid tailings are being treated, as is most generally the 
case, the neutral minerals having been almost completely used up, 
they should first be washed with water in order to remove the soluble 
salts, or " cyanicides " as they are called. This washing is done 
economically only when the analysis of the tailings or mineral shows 
a large amount of soluble salts. In some works, this is carried 
on in the cyani ding- vats themselves; but this is a very defective 
mode of treatment for these vats always retain on their walls a 
certain amount of cyanide, arising from a previous operation; this 
salt dissolves some of the gold and as these wash-waters are rejected 
it follows that there is a loss of precious metal. It is therefore 
better to do the washing in special vats, after which the mineral 
or the tailings are transferred to the cyaniding-vats. This washing 
is sometimes followed by another, this time using a caustic soda 
solution, containing 125 grams per 1000 liters of water, but it is 
generally better to mix the acid mineral with a certain amount of 


powdered lime before charging the cyaniding-vat, the amount of lime 
naturally varying with the quantity of cyanicides present in the min- 
eral (1 kg. per ton of very acid tailings or 250 grams per ton of tailings 
just from the battery). This method is more economical than that of 
caustic soda; lime is cheaper, and no special vat is necessary, the opera- 
tion being carried on in the cyaniding-vats. The results obtained are 
also better; by using soda the charged solutions become turbid and 
befoul the zinc which later is to be used for the precipitation of the 
gold, whereas with lime the solutions remain perfectly clear. 

When the mineral has been washed or treated with lime and 
been transferred to the cyaniding-vats, the cyanide solution, pre- 
pared as above stated, is added, covering the materials. The amount 
should be about one-third of the weight of the dry matter. This 
first solution is called " strong solution." Its strength naturally 
varies with the nature of the mineral, ranging from 0.25-0.80%. 
In the case of ordinary tailings a 0.30% " strong solution " is used; 
for acid tailings the strength of the solution varies from 0.25-0.50%. 
In many works 0.60-0.80% solutions are used. 

It should be mentioned that the selective action of cyanogen 
for gold grows in proportion as the solution is less concentrated; 
therefore the weaker the solution the less foreign metals does the 
cyanide dissolve. Therefore, the richer in heavy metals the mineral 
is the weaker the solution to be employed. 

The length of the treatment also varies, from 12-24 hours, accord- 
ing to the nature of the mineral. It is always well to remove a 
sample of the liquid from time to time in order to make sure of 
an artificial diffusion. In the case of minerals which require several 
days' treatment it is best to remove the whole of the solution after 
24 hours, and to add a fresh solution. And, in the case of certain 
concentrates requiring several weeks' treatment, the cyanide solu- 
tion should be renewed every 2 to 3 days. 

When the cyanide process was first used the mineral was kept 
constantly stirred in the vats, but it was soon found out that if 
this stirring did increase the yield somewhat, on the other hand the 
decomposition of the cyanide solution was hastened, besides entailing 
a considerable expense in motive power. Those are the reasons why 
this modus operandi was abandoned and in its place the percolation 
system just described adopted. 


By taking a sample of the solution and pouring it over zinc strips 
one can see whether the contact with the strong cyanide solution 
has been sufficient. If the metal grows dull the lixiviation is 

When the lixiviation is sufficient the solution is transferred to 
precipitation- vats by means of the cock and the pipe used in re- 
moving strong solutions, then a fresh cyanide solution, called "weak 
solution," containing only 0.15-0.40% potassium cyanide, is added 
to the mineral. The object is to carry away the gold remaining 
from the preceding treatment. Only half as much solution is used 
as in the first treatment, and the time of contact is only one to two 
hours. A third washing is made with the "weak solution' 7 and 
a fourth washing with pure water, which removes the last portions of 
the charged solution. The "weak solutions" are withdrawn by 
means of the cock and the tube used for that purpose and transferred 
to zinc boxes. 

At the Robinson works the treatment is somewhat different. 
The solution which has percolated into the false bottom of the vat 
is pumped on to the mineral of the same vat. Thus the extraction 
is more complete, and the amount of cyanide solution to be sub- 
jected to the action of zinc being smaller the losses of cyanides are 
appreciably reduced. 

Another modification consists in making the cyanide solution, 
which has already dissolved some precious metal in the first vat, 
flow from this first vat into a second, and then into a third, etc. 
The cyanided solutions thus obtained, containing more gold, give a 
purer precipitate of gold, and thus the losses in cyanide are likewise 

The amount of cyanide of potassium used in practice for the 
conversion of the gold to the form of gold-cyanide is always much 
larger than that required theoretically. Theoretically, 718 grams 
of potassium cyanide are necessary in order to dissolve 1 kg. of 
metallic gold; but in practice, in order to dissolve 7 grams of gold, 
contained in 1 ton of tailings, 350 grams of cyanide are required. 
That is a minimum seldom attained, except in special cases to be 
Studied later; generally 500 grams of cyanide are used per ton of 
tailings, and sometimes this amount is increased to 700, to 800 grams, 
and even to 900 grams in certain cases. 


De Mesenthal, who had opportunity to study the cyaniding proc- 
esses in the Transvaal itself, reports that for 1893 the Robinson 
Company used on an average 625 grams. In 1894 the amount of 
tailings treated at the Rand amounted to 1,200,000 tons, requiring 
the use of about 1200 of cyanide, or about 1 kg. of cyanide per ton 
of tailings. 

In de Wilde's process very weak cyanide solutions are used by 
means of a system of circulation and filtration which allows the use of 
only 105 grams of cyanide per ton of tailings containing 15 grams of 
gold. Small amounts of caustic soda are added now and then, which 
facilitates the solution of gold by preventing the action of atmos- 
pheric agents, carbonic acid, and waer from causing a decomposi- 
tion of the cyanide. In order to obtain perfect results, de Wilde 
recommends using red lead; Moldenhauer, using ferrocyanide of 
potassium; Kendall, sodium peroxid. 

Finally, two very similar processes for dissolving gold in potas- 
sium cyanide will be mentioned. The results which they pro- 
duce are quite vigorously disputed, and yet are little known. These 
methods certainly require a careful study, till now they have 
been tried only in few cases on a large scale, which fact does not 
permit of their being judged as to their industrial value. These 
are Sulman and Mulholland's bromo-cyanide mixed processes. 

The first consists in adding cyanogen bromide to the cyanide 
solution; the second yields the cyanogen bromide during the reac- 
tion and consists in simply adding bromine. The reaction may be 
thus expressed: 

4Au + 8KCN +2Br 2 +70 +H 2 =4KAu(CN) 2 +2KBr0 3 +2KOH, 
or in the case of cyanogen bromide, 

4 Au + 8KCN + 30 + H 2 = 4K Au(CN) 2 + 4KOH, 
4KAu(CN) 2 +4CNBr +4KOH =4KCNAuBr +4KCN +2H 2 +0 2 . 

As has been already remarked, the halogen acts only indirectly 
in order to set the necessary oxygen free. 

According to Mulholland, bromine displaces the cyanogen of the 
cyanide, which being set free reacts on gold, forming a cyanide 
of gold, which is then soluble in potassium cyanide, yielding auro- 


cyanide. Mulholland's process therefore consists in forming a 
gold compound more soluble in potassium cyanide than the metal 
itself. Bromine should not be in excess, otherwise potassium bromide 
and free hydrocyanic acid will be formed. In case this happens 
caustic soda or lime is added. Bromine may be added either all 
at one time or in small portions; the amount being previously deter- 
mined according to the percentage of precious metal in the minerals. 
This process yields 97% of the gold with the use of a smaller quan- 
tity of cyanide, and with greater ease and rapidity of solution. 

After precipitation with zinc the bromine may then be recovered 
without appreciable loss. 

Such are the chief methods used in carrying on the first part 
of the treatment of auriferous minerals by the cyanide process. 
Finally, as has been seen in this rapid review, these methods differ 
from each other only in the form and size of the apparatus. Never- 
theless, the methods have not yet reached perfection. It is evi- 
dent that the amount of cyanogen consumed is much too large, 
and the efforts and attention of chemists and manufacturers of 
gold districts should be centered on this point. 

It now remains to take up the second stage of the cyaniding 
processes that is the precipitation of gold from the cyanided solu- 

The methods are quite numerous, and will be taken up suc- 
cessively. These processes are of two classes: In the first gold 
is precipitated by metallic zinc; in the second by electrolysis. There 
exist other special processes, but they have had but few trials. 

Precipitation of Gold by Means of Zinc. The type of these 
processes is that of Mac Arthur and Forest. This is based on the 
fact that zinc displaces gold from its double cyanide as follows: 

2KAu(CN) 2 + Zn = K 2 Zn(CN) 4 + Au 2 . 

The zinc should have a special shape; as sheets the surface 
to be acted upon is too small; finely or coarsely granulated, or in 
powder, gives very unsatisfactory results. The best results are 
obtained with zinc in the form of shavings freshly prepared. 

These shavings are so prepared that they present a large sur- 
face. Thus 1 kg. of zinc in the form of shavings offers a surface 
of more than 8 square meters. 


Pure zinc is not suitable; only commercial zinc should be used, 
;such as contains some lead, which with the zinc forms a voltaic 
ouple which facilitates the reaction. 

The reaction goes on quite slowly at first, but just as soon as 
the gold begins to become deposited on the zinc, an electric couple, 
gold-zinc, is formed which greatly aids the reaction; but, on the 
other hand, the gold-zinc couple decomposes water by hydrolysis, 

2 0=Zn(OH 2 ), 

the zinc hydrate dissolving in the excess of potassium cyanide solution, 
Zn(OH) 2 +4KCN= K 2 Zn(CN) 4 +2KOH. 

This is one reason why the amount of zinc used much exceeds that 
indicated by the general reaction 

2KAu(CN) 2 + Zn = ZnK 2 (CN) 4 + 2Au. 

On the other hand, the alkali produced when the mineral is 
neutralized, or from the cyanide in which it is always present, and 
that which is set free by the action of the cyanide, together with that 
formed hi the reaction between zinc hydrate and the excess of 
cyanide all this alkali dissolves a fresh quantity of zinc, according 
to the reaction 

Zn + 2KOH= Zn(OK) 2 + H 2 ; 

potassium zincate acts on the double cyanide of zinc and potassium, 
Zn0 2 K 2 + ZnK 2 Cy 4 + 2H 2 = 2ZnCy 2 + 4KOH, 

which reaction prevents the liquors from becoming rich in zinc. 

In the presence of the excess of cyanide the reaction may be ex- 
pressed thus: 

4KCy + Zn + 2H 2 0=ZnK 2 Cy 4 +2KOH + H 2 . 

The reaction takes place as above, as the liberation of hydrogen 
may be noticed in the zinc boxes during the precipitation. Theo- 
retically this hydrogen should have a reducing action on the double 


cyanide of gold and potassium, setting gold free, according to the 

2KAu(CN) 2 + 2H =2CNH +2KCN +2Au. 

The reaction does indeed take place thus: Potassium cyanide is 
formed which is used in dissolving a fresh amount of gold, and metallic 
gold is precipitated. The hydrocyanic acid set free in the above 
reaction, coming in contact with the solution itself with an excess of 
potassa, unites with it in order to form potassium cyanide, 

2CNH + 2KOH = 2CNK + 2H 2 0. 

Finally, the liquor should necessarily contain an excess of zinc, 
which prevents the gold from redissolving in the potassium cyanide. 
Zinc combined with potassium has a greater affinity for cyanogen 
than gold combined with potassium has; therefore, when a solution 
of potassium cyanide is in contact with zinc it will not dissolve 
the precious metal. 

The precipitation of gold, as it is carried on at the works, will 
now be taken up. 

When the solution of potassium aurocyanide is withdrawn from 
the lixiviation-vats it is conducted into the zinc precipitation-vats, 
which are arranged in two series. One contains the " strong" solu- 
tions, the other the "weak" solutions. 

These vats are made of wood, and vary in size according to the 
works. As a rule, they are 6-8 meters long, 0.6-1.25 meters wide, 
and 0.7-0.8 meter deep. At the Robinson Company's works they 
are 6.6x0.6X0.6 meters. 

They are slightly inclined lengthwise, and divided into com- 
partments 0.50-0.60 meter long, so arranged that the solution 
passes from one compartment into another, first from the top, then 
from the bottom. In these compartments are small boxes or troughs, 
the bottom of whiih is a sieve made of iron thread 60 meshes per 
square decimeter and fixed on a movable wooden frame fastened 
by beams several centimeters from the bottom of the vat. 

In these troughs are placed the zinc shavings (about 18 kg. 
per compartment). At the head of the box a compartment is left 
empty in order that the slimes which may come from the lixiviation- 
vats may be allowed to settle, and likewise at the foot a double 


compartment is left empty, which serves to hold back the particles 
of gold carried away by the following liquid before it comes to 
the reservoirs. 

The charged solutions are allowed to flow through the com- 
partments at such a rate that in 9 hours about 60 tons of auro- 
cyanide solution, representing 225 tons of mineral, are passed through. 
In this way the loss of gold by being carried away is almost noth- 
ing. Gold is precipitated in the form of a blackish powder, which 
falls through the meshes of the sieve to the bottom of the compart- 
ment. The precipitation is generally incomplete if on emerging 
from the zinc boxes the solution contains more than 3 grams of 
gold per ton, in which case the operation has been badly con- 
ducted; on the other hand, if it does not contain more than 0.7 
gram the conditions under which the work is being carried on are 

In the first two compartments the reaction is quite vigorous; 
almost all of the gold is deposited; zinc is rapidly dissolved and 
is constantly replaced with shavings from the following compart- 
ments so that the last of these is always filled with fresh shavings. 

The zinc boxes are emptied twice a month. After adding water 
in order to remove the charged solution the sieves are withdrawn 
and shaken so that all the reduced gold which adheres to the meshes 
may fall to the bottom of the vats. The whole is allowed to stand 
for 1 hour, and when auriferous slime has been fully precipitated 
the clear supernatant liquid is siphoned off and transferred to a 

The walls of the vats are rinsed with pure water, and the mix- 
ture of water, gold, and pulverulent zinc is thrown on to a sieve, 
16 meshes per square cc. The mixture is stirred with a stick, the 
end of which is of rubber. In this way the zinc remains on the 
sieve while the slime containing gold, silver, zinc, lead, tin, anti- 
mony, etc., passes through. This slime is allowed to settle in a 
small vat, placed under the sieve, then dried in shallow pans. 

On the other hand, the zinc clippings which remain on the grating 
are washed and rubbed under water so as to remove as much as 
possible the gold which adheres to them. The grates are likewise 
brushed under water. After settling the water is decanted and 
the mud is added to that of the compartments. 


In certain works zinc boxes are used, fitted up with a longi- 
tudinal washer situated on the side of the boxes and communi- 
cating with each one of the compartments by openings ending below 
the grating. These openings, closed with a plug during precipita- 
tion, are used in allowing the auriferous slime to pass into the washer; 
the slime falls upon a filter where it is afterwards collected. Gener- 
ally the zinc boxes are covered with strong iron gratings which 
may be locked with a key. The auriferous slimes thus collected 
contain a large amount of zinc and of lead, some silver and copper, 
traces of antimony, arsenic, nickel, cobalt, aluminum, ferrocyanide 
of potassium and of zinc, cyanide of potassium and of zinc, cyanide 
of iron, sulphide of iron, carbonates of potash and lime, iron oxid, 
silica, etc. These are dried in shajlow pans, then they are roasted 
in order to oxidize the metals and to decompose the cyanides. 

This roasting takes place in small muffled furnaces on cast-iron 
dishes and at a dull-red 'heat, a temperature which should not be 
exceeded, the mass being gently stirred so as to avoid any loss of 
gold dust which is very fine. During this operation carbonic acid 
and ammonia proceeding from the decomposition of the cyanides 
are set free. In order to oxidize the zinc more easily it is advised 
to add 2-3% of potassium nitrate before the roasting. There 
is thus formed potassium zincate which is less easily reduced than 
the oxid of zinc. 

The roasted mass is then fused in the following way: 

An intimate mixture is made of the very dry auriferous pre- 
cipitate wish sodium carbonate or bicarbonate, borax, sand or 
fluorspar, in the following proportions: 

(I) Roasted auriferous slime 820 parts 

Carbonate of sodium 85 "'. 

Borax 55 ": 

Fluorspar 40 '1 

1000 ": 

(II) Roasted auriferous slime 100 ' r 

Bicarbonate of sodium 50 "'. 

Borax 25 " 

Sand.. 10 .": 


This mixture is placed in plumbago crucibles which are three 
quarters filled, and these are placed in a series of three in fusion 
furnaces. The mass fuses quite rapidly, a very fluid scoria being 
formed which acts on the crucibles to such an extent that they 
are soon out of order. As a rule they may be used for no more 
than six fusions. When the mass has reached the state of quiet 
fusion the crucibles are removed from the furnaces, and their con- 
tents poured into conical-shaped ingot moulds which have been 
previously rubbed with chalk so as to prevent the slag from 

The metallic portion being heavier falls to the bottom; after 
cooling the ingots are broken and thus the metallic bottom may 
be separated from the dross. 

The gold thus obtained averages 650 to 800 thousandths; it 
always contains zinc, lead, copper, and silver in variable amounts. 
Often the product from many of these operations is again fused with 
borax at as low a temperature as possible. 

Such, in a general way, is the process of Mac Arthur and Forest. 
Moreover, it differs from the others only in the method of precipita- 
tion, the cyaniding being done practically in the same manner in 
all the methods. As has been seen, in the precipitation by means 
of zinc there is formed potassium-zinc-cyanide, which involves an 
enormous consumption of potassium cyanide. In order to do away 
with this objection various methods have been proposed, the object 
being especially to recover the potassium cyanide which is partially 
lost in Mac Arthur and Forest's process. 

Andre, chemist of the Deutsche Gold and Silber Scheide Anstalt 
at Frankfort, proposed the use of aluminum instead of zinc, in which 
case the reaction is as follows: 

6K AuCy 2 + 6KOH + 2A1= 6Au + 12KCN + A1 2 3 + 3H 2 0. 

As is seen, the cyanide is in this way wholly reproduced, and 
on the other hand there is formed a precipitate of gold and alumina, 
the separation of which is rather easy. 

That is of an immense advantage, and Andre's process would 
certainly be adaptable to trial on a large scale if the cost of 
aluminium were not so great. 


Molloy's process consists in using a sodium amalgam according 
to the reaction 

HgNa + KAuCy 2 = HgAu + KCy + NaCy . 

The charged solution passes through a vat containing mercury, 
at the surface of which is placed a vertical cylinder containing a 
solution of sodium carbonate, and dipping slightly in the mercury 
bath. A sheet of lead dips into this solution. The mercury and 
the lead thus form two electrodes, united to the two holes of a bat- 
tery. Under the influence of the electric current sodium is formed, 

C0 3 Na 2 =C0 2 + + Na 2 , 

which unites with mercury, forming an amalgam, which latter decom- 
poses the aurocyanide solution yielding a gold amalgam and a solu- 
tion of sodium and potassium cyanide better suited to dissolve 
a fresh amount of gold. Molloy's process is not yet much in use, 
and the results produced by it are much questioned. However, 
this process deserves to be kept in mind. 

In 1894 Johnstone proposed making the potassium-aurocyanide 
solution flow on wood charcoal, which is afterward burned in order 
to extract the precious metal. At present no judgment can be 
rendered as to the value of this process, which, however, seems to 
present certain advantages worthy of consideration. 

Among the chemical precipitation processes worthy of attention 
that invented by de Wilde should be cited. It consists of three 
stages : 

(1) Solution of the gold by means of potassium cyanide. 

(2) Recovery of the excess of potassium cyanide. 

(3) Precipitation of the gold. 

The first operation, or the cyaniding of the mineral, is carried 
on in the same way as in Mac Arthur and Forest's process, with 
this exception (it has already been mentioned in the first part of 
this chapter), that in this case much weaker solutions of cyanide 
are used, for it is no longer necessary to use relatively strong solu- 
tions in order to avoid the incomplete precipitation by the zinc. 

When the gold has been dissolved in the cyanide the recovery 


of the excess of cyanide is immediately taken up. To do this 
ferrous sulphate is added to the solution, small portions at a time, 
with constant stirring. There is formed a precipitate, which at 
first is yellowish red but later becomes green, which is a double 
cyanide of iron and potassium, Fe 2 K(CN) 3 , the reaction being as 
follows : 

2S0 4 Fe +5KCN =2S0 4 K 2 +Fe 2 K(CN) 3 . 

The precipitate is separated by means of a filter-press, and 
allowed to stand in air, where it becomes rapidly converted into 
Prussian blue, [Fe(CN) 6 ]6(Fe 2 )2; this Prussian blue is then treated 
with a strong caustic potash solution, and is converted into iron- 
hydrate and potassium ferrocyanide, 

(FeCy 6 ) 3 (Fe 2 ) 2 + 12KOH =3Fe(CN) 6 K 4 +2Fe 2 (OH) 6 . 

The iron hydrate is filtered, the ferrocyanide filtrate being con- 
verted into cyanide by the ordinary methods. 

The ferrous sulphate should be added in slight excess, other- 
wise it would be detrimental. This is controlled by adding a few 
drops of ferri cyanide to the solution, and when this solution is colored 
blue, enough ferrous sulphate has been added. 

Before adding the ferrous sulphate the alkalinity of the solu- 
tion should be determined. It should be scarcely sufficient to turn 
litmus paper, for if it be too alkaline the addition of ferrous sul- 
phate will cause a precipitation of ferrous hydrate which would 
remove part of the gold. 

The precipitation of gold by de Wilde's process is based on the 
fact that if a solution of copper sulphate be added to the potassium 
aurocyanide solution, acidified with sulphurous acid, the potassium 
aurocyanide will be decomposed with formation of gold cyanide 
and copper cyanide, which are precipitated, as in the reaction 

2KAu(CN)2+S0 4 Cu=S0 4 K2+2AuCN+Cu(CN). 

The cuprous cyanide results from the action of sulphurous acid 
on cupric cyanide, Cu(CN) 2 , which is first formed so that the follow- 
ing is obtained: 

2Cu(CN) 2 +S0 3 H 2 =2CNH+S03+Cu2(CN) 2 . 


Either sulphurous acid may be used, or an alkaline bisulphite; 
this is added until a slightly acid reaction is perceptible. 

The copper sulphate should be added in slight excess if a com- 
plete precipitation is desired. The point of excess may be deter- 
mined by testing with potassium ferrocyanide, which with a cop- 
per salt gives a red precipitate of cupric ferrocyanide. 

The operation is carried on in large vats. The whole is allowed 
to stand for 10-12 hours, then the solution is decanted through 
the cocks, and the precipitate washed and dried. 

It is then ignited in order to convert the aurous cyanide into 
metallic gold and the cuprous cyanide into copper oxid, 

AuCy + Cu 2 Cy 2 + 2 = Au -f 2CuO + 3CN. 

The ignited product is then heated with sulphuric acid 60 B., which 
dissolves the copper, leaving the gold behind: 

Au +2CuO +2S0 4 H 2 =2S0 4 Cu + Au+2H 2 0. 

The copper sulphate is thus recovered. 

De Wilde's process has been applied with success in the Trans- 
vaal" gold districts by Loevy, and the results obtained have been 
in all points satisfactory, not only from the standpoint of 
economy but also from the completeness of the extraction. The 
following are some of its advantages: 

(1) Very much less consumption of potassium cyanide (5 or 
6 times less than in Mac Arthur and Forest's process). 

(2) The almost complete recovery of the excess of potassium 

(3) Likewise the almost complete recovery of the precipitating 
agent. These advantages the MacArthur process does not possess. 

Besides these methods, which are based on purely chemical reac- 
tions, are processes based on the use of electricity as a means of 
precipitating the gold. 

To Siemens and Halske of Berlin belong the honor of having 
.applied electrolysis to the extraction of gold from charged solutions. 

In 1887 Siemens noticed that the gold anodes used in his electro- 
plating works at Berlin lost in weight when they were left in the 


charged solution after the current was cut off. This phenomenon 
attracted the attention of the celebrated electrometallurgist, who* 
is justly called the pioneer of electrolysis, and he immediately sought 
to profit by it. 

In 1888 the first works for the treatment of auriferous solutions 
by electrolysis were established at Siebenburgen, and in 1889 other 
works were set up successively in Hungary, Siberia, and in America. 
At the present time Siemens and Halske's process is in regular opera- 
tion at the Worcester mines (in the Rand district) belonging to the 
Rand Central Ore Reduction Company, Limited. It is carried on 
in this way: 

The gold is dissolved by the aid of strong cyanide solutions 
0.06-0.08% and weak cyanide solutions 0.01%, in five large vats 
having a capacity of 75 cubic meters. 

The precipitation takes place in four vats, whose dimensions 
are 6x2.4x1.2 meters. The anodes are iron plates 3 mm. in 
thickness, 2.1 meters long, and 0.9 meters wide, dipping in the 
potassium-gold-cyanide solution, and held in a vertical position by 
means of pieces of wood placed on the bottom and on the lateral 
walls of the vats. One half of the anode dips to the bottom of the 
vat, while the other goes down to only 2.5 cm. from the bottom. 
In this way the vats are divided into a series of compartments 
between which the liquid flows alternately from down up and from 
up down. The anodes are covered with cloth so as to prevent short 

The cathodes are thin lead sheets. They are placed between the 
anodes and fixed on wooden frames which may be easily raised. 
The vats are covered with a cover locked with a key, and are opened 
only to collect the gold. 

The electric current is furnished by a Siemens dynamo of 8 volts 
and 600 amperes; it is 6 volts and 10 amperes per ton of mineral. 
Above 6 volts the cyanide is much decomposed. 

The gold is collected once a month. The vats are opened, and 
one by one the wooden frames supporting the lead sheets are 
removed and replaced by new ones. This requires but very little 
time, which is of great advantage as no interruption of work is neces- 
sary. The lead sheets upon which an adhering deposit of gold is 
formed, amounting from 2-12%, are melted and cupelled. 


During the precipitation of gold the iron anodes are attacked 
by the potassium cyanide, forming potassium ferrocyanide, which, 
reacting on oxid of iron formed, yields Prussian blue, and this is 
precipitated on the anode, thanks to a special coating with which 
this is covered. It is collected and treated as usual in order to con- 
vert it again into cyanide. 

Siemens and Halske's process fulfils the conditions stated by 
de Germet in his paper before the Chemical and Metallurg- 
ical Society of South Africa, which conditions may thus be re- 

(1) The cathodes should be of a metal to which gold sufficiently 

(2) This metal should be capable of being drawn out into thin 
sheets in order that the weight may be as small as possible. 

(3) It should be easy to remove the gold from it. 

(4) The cathodes should not be more electropositive than the 
anodes, so as to avoid the production of reverse currents when the 
current is shut off. 

Siemens and Halske's process has been much criticized, and 
different inventors have modified it in various ways. 

First is Keith's process (1895), in which the lixiviation is carried 
on with 0.01-0.5% solutions of cyanide, to which has been added 
double cyanide of mercury and potassium 60-300 grams per ton 
of solution. Gold, an electropositive element when considered in 
relation to mercury, decomposes the cyanide of this metal, setting 
cyanogen and mercury free. The latter unites with gold, forming 
an amalgam, but under the action of the voltaic couple gold is dis- 
solved and the thin film of mercury also dissolves in the cyanide, 
in order to reproduce the double cyanide, which may then act indefi- 
nitely. In practice, the operation is carried on as follows: On 
issuing from the lixiviation-vats the liquor passes into wooden 
boxes containing copper plates used as cathodes and arranged as 
in 'Siemens' process. Between these copper plates are placed por- 
ous jars containing a solution of ammonium chloride or sulphate, 
into which iron or zinc rods dip, these used as anodes. Under 
the action of the current, whose electromotive force is about one 
volt,^ mercury is deposited upon the copper plates, and it is upon 
these amalgamated plates that gold is later deposited. They are 


cleaned at regular intervals and without interruption, as in the Sie- 
mens process. 

Not having yet been tried on an industrial scale it is impos- 
sible to judge of the value of this process. Nevertheless its inven- 
tor claims as advantages: 

(1) The cyanide is not oxidized into cyanate. 

(2) Mercury facilitates the precipitation of gold. 

In Pfleges' process, likewise dating from 1895, the electrode on 
which the gold is deposited consists of metallic nettings sepa- 
rated about 1J-3 mm. and of about one thread per millimeter, 
presenting therefore a very large surface. The bath around the 
diaphragms consists of a 5% caustic soda solution, and includes 
zinc sheets, which with the netting form a sort of Daniell pile. The 
bath is divided by partitions which make it necessary for the soda 
solution to circulate in such a manner that the points of contact 
with the netting are increased. According to the author, the entire 
efficiency of the process is due to the great extent of surfaces which 
the metallic nettings offer for the deposit of gold. 

Finally, may be mentioned the method of Andreoli in 1897, 
and which is only a modification of Siemens' process, the used oxi- 
dized lead anodes, which, it seems, are entirely resistent. These 
anodes are obtained by placing sheets of lead into sodium plum- 
bate, washing them, and then plunging them into a solution of 
potassium cyanide, where, under the action of a strong current 
they become covered with a thin film of lead peroxide. 

The cathodes are of iron, and gold deposits on them in a closely 
adhering form. When the deposit of the precious metal is deemed 
sufficient, the cathodes are withdrawn and plunged into melted 
lead, into which the gold dissolves, and when the gold content of 
the alloy thus formed is high enough it is cupelled. By the use 
of oxidized lead anodes the formation of ferric compounds, which 
complicate electrolysis, is avoided. 

The yield and the net cost of these processes vary much accord- 
ing to the works and the nature of the minerals treated. 

Nevertheless in the Transvaal it is generally estimated that the 
MacArthur and Forest process gives an average extraction of 70 
to 75%, the net cost of treating one ton of tailings by this method 
being valued at from 8 to 9 francs. 


By Siemens' process, the average extraction is 70%, requiring 
113 grams of potassium cyanide per ton of tailings. The total 
expenses are only 3.75 francs per ton, and even 3.1 francs in some 

Among the other uses of potassium cyanide must be mentioned 
gold and silver electroplating. The objects, burnished and scoured, 
are placed in a bath containing 1 gram gold chloride or silver cyanide r 
according as it is gold- or silver-plating, and 10 grams of potassium 
cyanide dissolved in 450 grams of water. A gold or silver sheet is 
suspended at the positive electrode; it dissolves just as fast as the 
gold or silver of the bath is deposited on the objects placed at the 
negative pole, and thus the bath is kept constantly at the same degree 
of concentration. 

It is also used sometimes in reducing metallic oxides. 

It may be used in cleaning silverware which has become yellow- 
ish. A good formula for this purpose is the following: 

Distilled water 1000 parts 

Potassium cyanide 30 " 

Hyposulphite of soda 20 " 

Ammonia a sufficient quantity to give a decided alkaline 

Potassium cyanide was for some time used in photography, for 
fixing the negatives, on account of its property or dissolving gold 
and silver. It is now replaced by sodium hyposulphite, which has 
the great advantage of not being poisonous. 

It is used in the preparation of soluble garnet (potassium iso- 
purpurate) with picric acid, and in the preparation of cresylpurpuric 
acid with trinitrocresylic acid. 

It is recommended in medicine for combatting neurajgia and 
megrims (Trousseau). It is given in 0.50% lotions. 

Among the other cyanides sometimes used may be mentioned 
zinc cyanide, which is used in therapeutics as an antispasmodic;, 
silver cyanide used in silver electroplating, and mercury cyanide 
recommended as an antisyphilitic. 

Ferrocyanides. Potassium ferrocyanide is quite extensively 


A large portion (50%) of the ferrocyanide produced is used in 
the manufacture of potassium cyanide. The remainder is used in 
various ways in the arts and trades. It is used in the preparation 
of potassium ferrocyanide and of Prussian blue. 

It is employed in dyeing, where it is used in coloring blue and 
in weighting. It is frequently used in dyeing silk black with the 
aid of logwood and with aniline black. It is also much used in 
the production of steam colors. Of this Lyon consumes about 300 
tons annually. 

Ferrocyanide of tin, obtained by double decomposition of a 
tin salt and potassium ferrocyanide, finds quite extensive use in 
dyeing, in the production of white discharges as substantive colors, 
and in the production of certain steam colors added to the blues. 

The cementation of certain special steel (springs, tools, etc.), 
also requires the use of some ferrocyanide. In this respect we 
must mention the remarkable role which the cyanides play in cemen- 

In 1850, Caron demonstrated to the Academic des Sciences 
that the steeling substance in cementation was an alkali cyanide 
formed by the carbon used, the alkali contained in the ashes of this 
carbon and atmospheric nitrogen. By a remarkable series of ex- 
periments Caron proved that carbon without alkali or without 
nitrogen could not produce cementation, and that cementation was 
due to the formation of an alkali cyanide, an hypothesis confirmed 
by the fact that lime, which does not yield cyanide at the tempera- 
ture of cementation, does not produce this phenomenon. From this; 
Caron concludes that the most favorable conditions for a good 
cementation are those which permit the formation of cyanides. 

The cement, therefore, probably owes its activity to alkali or 
alkaline-earth cyanides which are formed during cementation, and 
if these cyanides are not the sole agents of the cementation they 
are, at least, the most important. But in all probability (experi- 
ment demonstrates this) they do not act because of the nitrogen 
which they contain, but simply as carriers of carbon. This property 
which the cyanides possess is due to a certain fixedness which does 
not permit them to give up their carbon except at the temperature 
at which cementation takes place. 

In certain works cementation is still superficially and rapidly 


done by means of wood-charcoal. Reaumur recommended as an 
excellent cement a mixture of wood-charcoal and sea-salt. Deep 
cementations are obtained with a mixture of 3 parts charcoal and 
1 part barium carbonate (barium cyanide being less volatile allows 
operating at a higher temperature, and for this purpose it is par- 
ticularly recommended by Margueritte and Sourdeval and Caron). 
Potassium ferrocyanide enters into the composition of a very 
explosive powder, the so-called white gun-powder, exploding by 
concussion or ignition. This powder was invented by Augendre, 
and was made of the following substances: 

Prussiate of potash 1 part 

Chlorate of potash 2 parts 

Sugar 1 part 

Pole has improved this powder and gives it the following com- 
position : 

Prussiate of potash 28 parts 

Chlorate of potash 49 " 

Sugar 23 " 

Its advantages over ordinary powder are: 

(1) It is not hygrometric, and keeps better than ordinary powder. 

(2) It produces more gas and leaves less residue than black 
powder, which leaves 68% solid residue, while the white powder 
leaves only 31 % The gas produced consists of a mixture of nitro- 
gen, carbon monoxide, carbonic acid, and water-vapor. The residue 
is composed of cyanide and chloride of potassium and a little iron 

(3) Its mechanical effect is a little greater. On the other hand, 
it has the serious objection of strongly oxidizing iron cannon, and 
at present it is scarcely used. 

Ferrocyanide powder is very sensitive to the electric spark. 

Potassium ferrocyanide is still sometimes used in therapeutics 
as a diuretic. It was formerly used as an antifebril, mixed with 
urea, but to-day it has fallen into complete disuse. 

Finally, potassium ferrocyanide is a very important and much 
used reagent in all laboratories. 


Ferricyanide. Red prussiate of potash is quite frequently 
utilized in dyeing and in printing, because of its very energetic 
oxdizing properties. 

It is used in the production of aniline black and violet. It 
converts aniline into Perkins' violet. It is likewise used in the 
production of steam colors direct from wood (logwood, Lima wood, 
Pernambuco wood, Brazilian wood) ; it gives either darker shades 
or converted print colors, puces, reds, violets. It has the advan- 
tage of not attacking the steel doctors, and does not copper the 
colors as do the copper salts. 

The printing of calicoes employs large quantities as discharges. 
Mixed with a soda or potash solution (Mercer liquor) it is used in 
producing white patterns on fabrics dyed in indigo blue. Likewise 
a mixture of nitrate of lead and potassium ferricyanide is a very 
powerful corroding agent. Finally, it is used in manufacturing 
special papers for photography and blue-prints. 

Prussian Blue This compound, which formerly was utilized 
to a great extent, is not much used to-day. The discovery of arti- 
ficial blues has completely dethroned it, and moreover the colors 
which it gives on fabrics, although they are fixed enough even on 
contact with acids, are, however, objectionable because they are 
not resistant to soap, and especially to alkalis. 

Coloring with Prussian blue is always obtained by the direct 
formation of the coloring substance on the fabric, by first fixing 
ferric hydrate on the fabric and then passing through a potassium 
ferrocyanide bath acidified with a mineral acid. 

Prepared Prussian blue is used in oil-painting, in the bluing 
and printing of papers and calicoes, and at present is especially 
used as a plastic color. 

Sulphocyanides. Sulphocyanide of potassium as such has no 
place in the arts and trades. It is especially used in the preparation 
of sulphocyanides of tin, aluminium, and copper, which are more 
or less used. Aluminium sulphocyanide is sometimes used instead 
of the acetate in printing steam reds and pinks. Not being acid 
as is aluminium acetate, it has the advantage over the latter of not 
attacking the steel doctors, and moreover of giving clearer and 
more brilliant reds than those of the acetate. Some tunes sulpho- 


cyanide of potassium is mixed with colors in order to avoid attack- 
ing, the doctors. 

Tin sulphocyanide, which is obtained by double decomposition of 
a commercial tin salt with ammonium sulphocyanide, is quite often 
used in printing cotton as acid discharges on direct colors. 

The canarine, a yellow color which is no longer used, is nothing 
more than persulphocyanogen, produced by the oxidation of potas- 
sium sulphocyanide. 

Ammonium sulphocyanide is also sometimes used in photography 
as a fixing agent. 

Mercury sulphocyanide was for some time used in the preparation 
of a toy known as Pharaoh's serpent and invented by Barnett in 
1866. When this salt is mixed with potassium nitrate and lighted, 
it puffs up and twists and winds about, making it appear like a 
serpent. This phenomenon is due to an abundant liberation of 
nitrogen and vapors of carbon bisulphide and mercury. This toy 
is rather dangerous, as mercury sulphocyanide is a very poisonous 
compound. Moreover, the same results may be obtained by oxidiz- 
ing with nitric acid the residue of the purification of brown coal- 
oils (Vorbringer). 

Sulphocyanide of copper is much used in the preparation of sub- 
marine paints. The coat applied to the hulls of ships prevents by 
its toxic properties the crustaceans from adhering to the vessel. 

Potassium or ammonium sulphocyanide is frequently used in the 
laboratories in testing for ferric salts, or for the presence of nitrous 
compounds in nitric acid. 

Among the other cyanide compounds that can be used may 
also be mentioned calcium cyanate, which a few years ago was 
highly praised as a fertilizer by Camille Faure, and hydrocyanic 
acid, sometimes used in medicine in pulmonary diseases, and those 
in which inflammation is seriously induced, such as asthma, whoop- 
ing-cough, etc. 


FROM the technical and economic study which has just been 
made, it follows that the cyanide industry has been improved in a 
remarkable way, especially in the last fifteen years, and that it is 
now in a most interesting period of progress. 

As we stated at the beginning of this work, the increase in the 
demand has been the chief cause of these improvements. 

At the present time the old processes, i.e., those based on the 
use of nitrogenous organic substances, are only used in rare cases. 
Cyanides are now produced almost wholly: 

(1) By new processes, known as synthetic processes. 

(2) By illuminating-gas and the residues produced in its manu- 

The question naturally occurs to one, Of all these processes 
belonging to one or the other category, which is or which are the 
best? This question is very hard to solve. Nevertheless, by 
relying on the results obtained, it may be possible to a certain 
degree to answer that question and that is what will now be 

The synthetic processes have the great advantage of producing 
potassium cyanide as a final product. But in most of these processes 
this advantage is counterbalanced by serious objections: the tem- 
perature required for the reaction is often very high, from which it 
follows Hi at losses by volatilization occur, besides a rapid wear and 
tear of the apparatus. Moreover, the conversion is very often 
incomplete, and the reactions do not always take place as simply 
as the theory would lead one to expect. Notwithstanding the 
numerous efforts of investigators and manufacturers, very few of 
these processes have had any really practical application. Not one 



of the synthetic processes using nitrogen and alkali metals has yet 
given satisfactory results. At one time great hopes were placed 
on the processes which consisted in making atmospheric nitrogen 
act on metallic carbides; works had even been established at Frank- 
fort, but the results never came up to expectations, and according 
to information, this method of manufacture is now abandoned, or 
is on the point of being abandoned. 

On the other hand, the methods using ammonia appear to give 
satisfactory results. Among those which still use the oxids or 
carbonates of the alkalis, two only deserve to be kept in mind: 
those of Roca and of the Stassfurter Chemische Fabrik. The latter, 
however, established on a large enough scale, seems to give rather 
unsatisfactory results. 

Only the methods which start with an alkali metal (sodium), 
carbon, and ammonia, with the intermediary formation of cyanamide, 
seem to have succeeded. The results obtained by the Deutsche Gold 
und Silber Scheide Anstalt confirm this statement. The one serious 
objection is the relatively high cost of metallic sodium or its alloys. 

The synthetic processes have been developed especially in Ger- 
many and England, and that is the reason that the cyanide industry 
has become so important in those countries, and that they are able 
to deliver these products much cheaper than others. 

The second class of methods for the production of cyanides, 
which consists in the extraction of cyanogen compounds from the 
residues of the manufacture of illuminating-ga or from gas itself, 
cannot, properly speaking, be considered as a means of manufacture, 
as it is but an adjunct of the gas industry, on which it depends 
absolutely. Nevertheless, if gas manufacturers could see what 
benefits there are to be derived from it, it would constitute a profit- 
able and important source of the cyanide production, and probably 
might provide for a great portion of the demand. This class of 
processes may therefore be of great service, especially if one con- 
siders that these compounds form themselves, and that without 
injuring the quality of the gas produced, the manufacturer may 
still increase the amount of cyanogen compounds; and, finally, that 
their recovery is made with very little expense. 

The processes which extract the cyanogen from the gas directly 
are those which appear to give the best results, economically as 



well as from the standpoint of yield, and among these the processes 
of Julius Bueb seem to have an important future industrially on 
account of their simplicity and the very satisfactory results which 
they furnish. 

It is true that the gas industry yields only ferrocyanides which 
it is then necessary to convert into sodium or potassium cyanide. 

As we have seen, this conversion is done very simply by the 
Rossler-Hasslacher Co.'s process; that is, by means of metallic 
sodium. This process is practically the only one now in use, and 
it gives excellent results. When the price of sodium does not exceed 
250 francs per 100 kg., this process is profitably conducted, otherwise 
not. This same statement also applies to synthetic processes using 
this metal. 

Another class of processes very similar to those based on the 
manufacture of gas is that which consists in converting the nitrogen 
of the sugar-beet vinasses into cyanides. As is well known, the 
sugar industry has grown enormously in Germany and France, 
and it has been seen that the dry distillation of vinasses may 
profitably produce cyanides. Here again, the discoveries of Bueb 
of Dessau seem to give the best results; therefore it is to be hoped 
that soon all the manufacturers, distillers, or gas-makers will know 
in France, as well as in England and Germany, how to derive all 
the "cyanogen which their industries are capable of producing, and 
that under the simplest and most profitable economic conditions. 




Weight per Liter. 


1 8064 

2 335 (0 at and 760 mm ) 

' ' liquid 

/ 0.866 at 17. 2 

Hydrocyanic acid (anhydrous 
liquid) . 

I . 706 at 7 
JO. 7058 at 7 
\ 6969 at 18 

Hydrocyanic acid, gis . . 


1 210 (at and 760 mm ) 

Ammonium sulphocyanide. . . 

Potassium cyanide 
ferrocyanide .... 

(1.3075 at 13 Clarke) 

sulphocyanide. . . 
Sodium nitroprussiate, crys- 





Temperature. Tension of Conversion. 

502 54 mm. 

559 123 " 

575 129 " 

587 . 157 " 

599 275 " 

601 318 " 

620 868 " 

640 1310 " 


Heat Liberated, the Compound being 
Name. Components. 

Gas. Liquid. Solid. Dissolved. 

Potassium cyanide CN + K + 67 . 6 64 . 7 

.Sodium " CN + Na +60.4 +59.9 

Calcium " CN + Ca +57.7 

Barium " CN + Ba z-4.3 z-3.4 

Zinc " CN + Zn +29.3 

Mercury " CN + Hg +11.9 +17.9 

.Silver " CN + Ag + 3.6 



Hydrocyanic acid CNH 5.7 

Cyanogen chloride .CNC1 -8.3 

1 MOL.=22'.22(l + otf) AT 760 MM. 

Hydrocyanic acid +6.1 

Cyanogen +6.8 

Critical tern. Atmospheric pressure. 

124. 0. .:.-, . 61 7 



Ci Ci * TH 1C W 1-1 Tt< l> Oi Ci rh 00 !> O5 N. r-t 

D Ci CO 

CO !> CO CO O rH CO l> Tt< O5 CO O CO Ci O5 .-I I> CO CO C5 tO 

'*"**"* I -I ^ " I 1-1 

(N iCCO COTt< T^ Oi OO 00 i-i 

1 1 1 1 1 1^^^^8^^'g^ ISS \%%%% | 
+++++ i +++ + ++++ 

00 10 <N Oi 

1 Igj^^i^ 1 1 1 1 1 1 1 1 ! 1 1 1 1 1 1 i II 
i + i + 

CO tO IQ 00 I> CO 

'^^\ I II 1 1 1 1 1 1 1 1 1 1 1 I II 

I I + I + 

IO IO i-H i-l 1-H 

CO<Ml>I>i-I T H^^iOtOO5COCOi-irHOi 
<M tO (N (N CO CO * Tt^ CO O Tji <M (N QO 00 O 

(N (N 



W S df M 







^ -2 
^ ^ 

I 1 



^ g 




T-ITH l>O5rt< T* 

l> CO 


t> Oi t>i-H 

AV 4^^ ^, I i I T-H I O^ Oi ^H t>- 

^^H0 eq CC^HOOt- 

i-H l-H I ' I ' 

I + 

O* CO CO CO .T}* 

&R is 

^H CO ' i-( 

1 1 r- 

CD O CO rt< O5 O 00 O CO 1C 00 (N O rfi CO (M O 

<N il^ iCCCOcCcDiCcO il>t^T-iO 

1> | 00 ICOT^T-IOCCIO |lCr-*rHC^ 


1 1 1 1 1 1 1 

1 1 1 1 

I i ! 


^^^' I I I I I 

I + I ' 

+ 02 rr> & & & & ^>> 

^o-M55^5 t S^? + ^ + + + +00 ^ 

+ + + + + + + +,+ + + + + 

asal P 


i^miillli jinliiijilr ' 








1i !i 

02 <- 

Q fc 

I 2 


^OJ S 

,O ^ >> 

3 - T! 



S rf I 

l.s l. a 

H *^ ^^ rH 

,-g ^ fl 


-2-^ ^ 

; & 




^ rj 3 (w O) 
B B*S O O 

.2 ^ 
^ 'Scs 

s si 








s .| | .-.iji 



rdy precipi 





5 S-e' 







Mercury cyanide 20 B. 

Potassium ferrocyanide 38? " 

Ammonium sulphocyanide 18 " 

A mixture of 

Ammonium sulphocyanate 133 

Water 100 

produces a lowering in temperature of 31 (Ruddorf). 


4KOH +54.0 cal. 

,, n 2BaO. +56.0 " 

FeCy 6 H 4 dissolved^ ^^ ; +4g g 

|Fe 2 3 ppt +25.2 " 

Fe 2 Cyi 2 H 6 dissolved +6KOH +58.0 " 

fKOH. .../. +14.0 " 

CySHdissolved + ( ^ +12 5 M 


C 2 + N 2 , 262.5 cal. 

C + N + H 158.0 cal. (gas) 





Per Cent. Potassium 






Per Cent. Potassium 








Per Cent. CNH. 



























Per Cent. Potassium 






















Density at 15. 

Per Cent. CNS . NH* 





















THIS digest covers most of the patents included in the following classes and 
subclasses of the United States Patent Office classification: 

Class 75. Metallurgy. 

Subclass 18. Solutions and Precipitation. 

Subclass 86. Solutions and Precipitation Apparatus. 
Subclass 185. Cyanides. 

Class 204. Electrolysis. 

Subclass 15. Aqueous Bath, Ores. 

Some of the patents in these categories are quite foreign to the subject under 
consideration, and many but indirectly related to it. It has been thought, how- 
ever, from the form which discussions of patent issues often take, to include the, 
latter. The aim in making the digest has been to give such a sketch as will indi- 
cate the nature of the invention and what is claimed by the inventor, this gen- 
erally being done by an acttial abstract from or paraphrase of the words of the 
letters patent, but no responsibility is assumed for the opinions, theories, or claims 
thus set forth. Other related patents may have been granted which do not appear 
in this digest, because they are not embraced in the subclasses enumerated. Thus, 
the patents number 229586, to Thomas C. Clark; 236424, to H. W. Faucett; and 
244080, to John F. Sanders, do not appear in this digest, because the first two are 
classified under subclass " Reducing and Separating Disintegrating Ores," and 
the third under subclass " Reducing and Separating Gold and Silver J1 and neither 
of these subclasses is included in this digest. 


1551,2 August 12, 1856. W. ZIERVOGEL. Improvement in processes of separa- 
ting silver from the ore. The application of water or a solution of sulphate of cop- 
per slightly impregnated with sulphuric acid instead of lead, quicksilver, or salt, 
hitherto used for this purpose, to the process of separating silver from copper 
and other ores, rendering thereby this separation easier, shorter, less expensive, 
and not noxious to the health of the operator. 

* Reprinted from " Precious Metals Recovered by Cyanide Processes " by Charles E. Munroe, 
Ch. D with the kind permission of the Department of Commerce and Labor. 



19991 April 20, 1858. I. GATTMAN. Improvement in the treatment of sul- 
phureted ores. The use of sulphuric acid in connection with the hydrate, car- 
bonate, or sulphate of potash or soda, or with any compound thereof, in the mode 
of working the native metallic sulphurets. 

3584.2 July 8, 1862. J. SHAW. Improved apparatus for saving silver from 
waste solutions. Attaching to the waste pipe of the sink or basin into which per- 
sons using silver in solutions suffer them to be wasted, a vessel so arranged and 
constructed that the liquids passing from the sink shall run into, through, and 
out of said vessel, and between the time of entering said vessel and escaping there- 
from shall be brought into contact with such chemicals or metals as will cause 
the whole or any part of the silver contained in solution to be precipitated and 
retained in said vessel, while the worthless material is allowed to escape. (This 
patent was reissued as follows: Reissue 1651, April 5, 1864; reissue 3506, June 15, 
1869; reissue 4030, June 14, 1870; reissue 4969, Division A, July 9, 1872; and 
reissue 4970, Division B, July 9, 1872.) 

46875 March 21, 1865. W. BRUCKNER. Improved process for refining amal- 
gam. The application and use of bichloride of copper, or its equivalent, together 
with iron pyrites and salt, without reference to the exact proportions of each 

46983 March 28, 1865. G. W. BAKER. Improvement in treating ores. In 
order to produce a valuable metal or metals now almost wholly cast away in the 
treatment of auriferous and argentiferous pyrites, the inventor proposes to take 
the calcined ores as they come from the furnaces, and, having them weU pul- 
verized, subject them to the action of sulphurous acid in tanks located over the 
main discharge flues of his furnaces, whereby a sufficient heat may be obtained 
to assist in the reaction of the acid before mentioned. The sulphurous acid thus 
used is to be formed and collected by compelling the sulphurous vapors discharged 
from the roasting furnace to pass over, through, and in contact with water, so 
that sulphurous acid will be formed and collected in a properly arranged tank 
or tanks, from whence it may be conveyed to the ore tanks, and there mixed with 
the ore thoroughly by agitation in any manner most convenient. After the ore 
has been subjected to the action of the acid for a couple of hours the oxide of cop- 
per will be replaced by a sulphate soluble in water, and the oxide of iron will be 
partially brought into the same condition Should there be any gold or silver 
held in solution these metals will be reduced to the metallic state. The solution 
is then drawn off by siphon or otherwise and conveyed to another tank or vat 
for subsequent treatment, either by cementation or precipitation for the copper 
and evaporation for the sulphate of iron. The ore thus treated may then be 
lixiviated by water to wash out all the acid, and this water, which will still hold 
some dilute solution of the baser metals, may be conveyed to the acid tank and 
used for the further formation of sulphurous acid. By this means the most con- 
centrated solution is alone permitted to pass to the tank or vat for further treat- 
ment. It may be considered a well-settled fact that in all processes of calcina- 
tion some portion of the precious metals, if such ores are under treatment, escape 
mechanically or in a vaporized form. This loss, great or small, as the case may 
be, has heretofore been to a great degree irreclaimable. It is claimed as a part 
of this improvement that such loss, whether mechanical or in the form of vapor, 
is wholly prevented by arresting their escape and returning them, either in solu- 
tion or in the sediment of the liquid acid, to the ore when treated in the ore tanks. 

? April 18, 1865. W. L. FABER. Improved process of working silver 
ores. The invention consists in a process which is divided in eight different manipu- 
lations, viz., smelting the ore, pulverizing, roasting at low heat, extracting sul- 
phates with water, roasting residue with salt, melting with soda, precipitating 
silver, precipitating copper. 

49637 August 29, 1865. S. F. MACKIE. Improved process for treating ores. 
The mode of obtaining a rich gold residue from ores of gold by treating the ores 
by roasting and fusing, and subjecting the roast to the action of acids. 

52834 February 27, 1866. J. H. ELWARD and J. L. HAYES. Improved process 
for separating gold and silver from ores. The process of oxidizing sulphurets con- 


taining the precious metals and converting them into sulphates by the use of solu-. 
tions of nitrates. 

56765 July SI, 1866. E. LAMM. Improved method of preparing gold for 
dentists. The use of saccharine substances to precipitate gold from its solutions, 
thereby forming a mass of crystal shreds extremely useful and convenient for 
dental and other purposes. 

148356 March 10, 1874- J. DOUGLAS, Jr. Improvement in extracting silver 
from its ores. The process of utilizing the waste liquors of the ordinary ore-chlori- 
dizing process, by allowing the insoluble matters contained in said liquors to pre- 
cipitate, and then evaporating the clear supernatant liquid to obtain the soluble 
chlorides, which are reapplied in treating fresh ores. 

207695 September 3, 1878. J. TUNBRIDGE. Improvement in separating metals 
from waste solutions. The process of separating precious metals from watery 
solutions, in which said metals are suspended by passing the watery solutions 
or puds through a bath of oil or hydrocarbon liquid. 

219961 September 23, 1879. F. M. LYTE. Improvement in extracting metals 
from ores. In the treatment of ores containing lead, zinc, silver, and copper, the 
method of securing the neutralization of the solutions of soluble bases, economizing 
acid, and carrying over the least possible quantity of silver and lead, which con- 
sists in treating the raw ores with an acid solution partially saturated by previous 
attack on the ores, and treating the partially exhausted ore by raw acid before 
the latter is admitted to the raw ore, the said steps being conducted in a continu- 
ous, alternate, and methodical manner. 

227963 May 25, 1880. W. M. DAVIS. Depositing gold from its solutions. The 
process of obtaining gold from its solution by bringing said solution in contact 
\/' with carbon, and thereby depositing the gold upon it, and of subsequently obtain- 
ing the gold from the carbon by calcination or other equivalent means. 

287737 October 30, 1883. C. A. STETEFELDT. Process of treating sulphides. > 
The process of treating sulphides, such as those obtained from the lixiviation process 
of silver ores, said process consisting in first exposing said sulphides to the action 
of dilute sulphuric acid in the presence of nitrate of soda, then converting the 
nitric oxide which escapes into nitrous acid and nitric acid, and finally carrying 
on the process by means of a mixture of nitrous acid and nitric acid with dilute 
sulphuric acid. 

288838 November 20, 1883. J. MILLER. Process of recovering metallic particles 

from water. The method of recovering metals in suspension in liquid, consisting, 

\ essentially, in forcing such liquid through a filtering medium having a capacity 

^" of expansion, and resisted by a rigid inclosing vessel or medium, and then burning 

the filling material or otherwise separating the metal therefrom. 

290258 December 18, 1883. J. MILLER. Apparatus for collecting and saving 
metallic particles. An apparatus for recovering metals or metallic compounds in 
X/" liquids, consisting of a rigid tank, perforated on one side, in combination with 
an entrance pipe, provided with a trap and a pressure device. 

290458 December 18, 1883. J. MILLER. Method of recovering metals. The 
improved method for recovering metallic particles, slimes, and similar material 
containing metal from liquids, consisting, essentially, in conducting the liquid 
and metal-bearing material to a settling tank, allowing the gangue to fall to the 
bottom, drawing off the liquid, and forcing it under hydrostatic pressure through 
a filter press, and removing and drying the filtrate. 

292605 January 29, 1884. C- P. WILLIAMS. Art of extracting gold by means 
of alkaline sulphides. In the art of extracting gold from ores and artificial gold- 
\f bearing products by means of alkaline sulphides, the process, which consists in 
mixing the gold-bearing material with carbon and an alkaline sulphate (or the 
equivalents of sucii carbon and alkaline sulphate), calcining said mixture in a 
non-oxidizing atmosphere at a temperature below the point of fusion of the charge, 
cooling the mass out of contact with the air, and leaching the cooled mass with 
water to dissolve out the soluble sulphides, and recovering the gold therefrom by- 


877809 February 14, 1888. T. KIDDIE. Process of separating precious metals 
and impurities from solutions of copper, salts, ores, mattes, etc., in acids. The process 
of removing precious metals and impurities from copper mattes, ores, bullion, 
etc., consisting in dissolving the same after desulphurization and calcination in 
sulphuric acid, in quantities sufficient to form a neutral solution, and in adding 
iron hydrates to the neutral solution, whereby the impurities are precipitated 
and settle with the precious metals not dissolved by the sulphuric acid, leaving 
a comparatively pure solution of iron and copper salts. 

881809 April 84, 1888. R. OXLAND and C. OXLAND. Treatment of ores and 
materials containing sulphur for the extraction of metals and other constituents, The 
method of treating raw or unburned sulphuret ores of copper and iron to render 
the copper soluble in water, while leaving the iron for the most part insoluble and 
rendering the sulphur in the ore available for the manufacture of sulphuric acid, 
consisting in mixing the finely pulverized ore to a semifluid consistency with sul- 
phuric acid and solution of persulphate of iron, heating the mixture to a tem- 
perature such as to evolve sulphurous-acid vapor, and collecting and condensing 
isuch acid vapor. 

887688 August 14, 1888. A. H. Low. Extraction of zinc from ores. The 

Srocess of extracting zinc from ores containing precious metals, consisting in leach- 
g the ore with an aqueous solution of sulphurous-acid gas to dissolve out the 
zinc, and then boiling the leached liquor to expel the sulphurous-acid gas and 
cause a precipitation of the zinc. 

403615 May 21, 1889. E. H. RUSSELL. Process of leaching ores with hypo- 
sulphite solutions. The process of extracting metal from ores and metallurgical 
products, which consists in introducing into the ore or product carbonate of soda, 
then treating the mass with a solution of sulphate of copper, and then treating 
it with a hyposulphite solution. 

413808 October 29, 1889. J. S. MACARTHUR. Process of leaching ores. The 
process of treating ores containing oxides or carbonates of earth metals, consist- 
ing in first subjecting such ores to the action of a proportionate quantity of a solu- 
tion of a ferrous salt or a bisulphate of an alkali to combine with the oxides or car- 
bonates of earth metals, and then treating the ores with an acid or salt to obtain 
the contained metals. 

[ February 11, 1890. R. PEARCE. Process of extracting silver from 
copper ores, mattes, and other copper products. The process of separating silver 
from ores or mattes containing base metals, which consists in mixing with the 
finely pulverized ore or mattes a quantity of sulphate of sodium or potassium 
/ equal to 2 per cent., then roasting the mixture, and finally leaching out by hot 
water to obtain the sulphate of silver. 

440143 November 11, 1890. E. DODE. Process of separating gold and plati- 
num from other metals in solution. The process of separating from an acid solu- 
tion of gold, platinum, copper, and tin the metallic constituents of said solution, 
which process consists in first subjecting the entire solution in the presence of 
ether to agitation until the ether becomes yellow, in then decanting the remaining 
solution from the yellow ether, in then subjecting said remaining solution to agita- 
tion in the presence of essence of lavender until the essential oil becomes brown, 
.. and in then decanting from the brown essential oil the remaining solution and 
e adding thereto ammonia. 

442016 December 2, 1890. C. L. COFFIN. Process of treating ore containing 
lead, silver, and zinc. The process of treating ore containing lead, silver, and 
zinc to remove the zinc preparatory to smelting, consisting in first roasting the 
ore, then leaching the ore, filtering the leach fluid through carbon, then subject- 
ing the leach fluid successively to the action of metallic lead and of metallic zinc, 
and finally precipitating the zinc held in solution in the leaching fluid. 

444997 January 20, 1891. W. WEST. Process of treating zinc ores. The 
process of eliminating zinc from complex ores, which consists in roasting the ore 
to form sulphurous-acid gas and oxidize the zinc, then cooling this gas to a tem- 
perature of 180 F. or below, and passing the same in gaseous form in conjunction 
with steam and without oxidation into sulphuric acid through a previously roasted 




charge to form soluble sulphite of zinc, and then immediately leaching out and 
separating the zinc sulphite with water at a temperature below 180 F. 

449814 April 7, 1891. S. W. CRAGG. Lixiviation process of and apparatus 
for the extraction of gold or silver. The process of restoring the oxygen in a hypo- 
sulphite solution in the lixiviation process, which consists in passing a current of 
air through the ore pulp while the said solution is in contact therewith, and a 
leaching vat, a grating at the top thereof through which ore pulp and water are 
introduced to the interior of the vat, and a system of crossed separated bars within 
the vat through which the ore pulp and water pass, combined with an endless- 
apron filter on which the ore pulp and water fall from the said crossed bars, a,trough 
beneath the filter to receive the water, and a lixiviation vat into which the apron 
filter discharges the ore pulp. 

471616 March 29, '1892. J. LEEDE. Process of treating refractory ores. The 
continuous process of treating refractory auriferous and argentiferous ores, which 
consists in subjecting the ore to the continuous action of an oxidizing blowpipe 
flame in direct contact with the ore at a moderate heat, intermittently subjecting 
the heated ore to the action of .water, agitating the ore, and then repeating the 
operation at a higher heat, and finally subjecting it to an oxidizing roast without 
chills, whereby the volatile elements are driven off, the oxidizable elements or 
compounds are oxidized, and the precious metals are left free and in suitable con- 
dition for amalgamation or chlorination. 

473186 April 19, 1892. P. C. CHOATE. Method of producing metallic zinc. 
The process of producing metallic zinc from its ores, which consists in separating 
the zinc and the equally volatile and more volatile constituents from the less vola- 
tile constituents of the ore by the use of heat and a reducing agent, then volatiliz- 
ing and oxidizing the reduced metal, thereby obtaining a condensed oxidized 
fume, subjecting this fume to a moderate heat in order to expel its soluble con- 
stituents more volatile than zinc, treating the remaining product with dilute sul- 
phuric acid as a solvent, and finally subjecting the resulting solution to the action 
of an electric current to precipitate the zinc. 

481499 August 28, 1892. G. T. LEWIS and C. V. PETRAEUS. Process of 
treating sulphide ores of zinc and lead. The process of recovering lead and zinc 
from sulphureted lead and zinc-lead ore, which consists in roasting the ore, then 
smelting the roasted mass* and exposing the fumes or volatile matter produced 
by said smelting to the action of the gases which are volatilized in the roasting 
of said ore, together with water, and then separating the zinc solution from the 
insoluble lead compound and recovering the zinc and lead. 

483924 October 4, 1892. T. S. HUNT and J. DOUGLAS. Process of separating 
copper from cupriferous nickel ores. The method of separating the copper from a 
solution containing copper oxide and oxides of iron and nickel to produce nickel- 
iferous iron, which consists in first adding common salt to the said solution, then 
passing a stream of sulphurous-acid gas through the said solution, then precipi- 
tating the last traces of the copper in the form of metallic copper, and subsequently 
crystallizing out the nickel and iron and calcining and smelting the product to 
obtain nickeliferous iron. 

483972 October 4, 1892. C. WHITEHEAD. Process of treating mixtures con- 
taining sulphides of precious metals and copper. The process of treating a mix- 
ture containing sulphides of the precious metals and of copper, which consists 
in mixing the sulphides with solution of a salt of silver, whereby a soluble salt 
of copper is formed and sulphide of silver is precipitated, separating the solution 
containing the copper from the residue containing the precious metals, roasting 
this residue to reduce the precious metals to the metallic state, treating the 
reduced metals with hot sulphuric acid to dissolve the silver, separating the silver 
solution from the residue, and melting the final residue. 

490068 January 17, 1893. F. P. DEWEY. Process of treating mixtures con- 
taining sulphides : The process of treating mixtures containing sulphides of silver 
and copper, which consists in heating the sulphides with strong sulphuric acid 
to convert the sulphides into sulphates and dissolve the sulphate of silver, adding 
water, to bring the sulphate of copper also into solution, drawing off the resultant 


solution, precipitating the silver therefrom by metallic copper, and recovering 
the sulphate of copper from the remaining solution. 

490193 January 17, 1893. A. FRENCH. Process of obtaining gold, silver, 
and copper from ores. In processes for obtaining gold, silver, and copper from 
ores, the treatment of the ores by pulverizing, mixing therewith small percentages 
of niter cake or bisulphate of soda and common salt, furnacing at a red heat, and 
then leaching. 

497473 May 16, 1893. W. R. INGALLS and F. WYATT. Process of treating 
complex or sulphide ores. The process of treating complex sulphide ores, which 
consists, first, in subjecting the ore to a sulphatizing roasting; second, lixiviating 
the roasted ore with water and sulphuric acid and removing the iron therefrom 
if necessary; third, precipitating the zinc from said solution in the form of car- 
bonate or carbonate and hydroxide by the use of sodium carbonate and subse- 
quently converting the same into zinc oxide; fourth, evaporating the sodium 
sulphate obtained from the zinc sulphate solution and heating the same with sodium 
chloride and coal to convert it into sodium sulphide; fifth, converting the sodium 
sulphide into bicarbonate of soda by dissolving the same in water and treating the 
solution with carbonic acid gas; and lastly, converting the bicarbonate of soda 
into sodium carbonate by heating the same to drive off the hydrogen and car- 
bonic acid gas. 

609058 November 21, 1893. E. WALLER and C. A. SNIFFIN. Method of 
concentrating ores. The method of concentrating argentiferous lead carbonate 
ores, which consists in dissolving out lead from the ore with the aid of acetic acid 
real or combined, and water, out of contact with the air whereby the lead and 
carbonic acid eliminated from the ore are rendered capable of utilization in the 
arts, and the undissolved silver is concentrated in the residue. 

509633 November 28, 1893. D. K. TUTTLE and C. WHITEHEAD. Process of 
treating precious metal-bearing slimes. The process of treating precious metal- 
bearing slimes, which consists in subjecting the slimes to the action of dilute acids 
to dissolve the metals and oxides soluble therein and to the action of a solution 
of a salt of silver to remove metals more electro-positive than silver that are present 
in the metallic state. 

509634 November 28, 1893. D. K. TUTTLE and C. WHITEHEAD. Process 
of refining slimes from the electrolytic refining of copper. The process of treating 
slimes from the electrolytic process of refining copper, which consists in removing 
arsenic, antimony, tellurium, bismuth, and other impurities present as oxides by 
treating the slimes with dilute acid and heating the purified slimes with strong 
hydric sulphate. 

513490 January 30, 1894. S. H. EMMENS. Process of treating zinc-lead-sul- 
phide ores. The process of treating zinc-lead-sulphide ores carrying gold or silver 
or gold and silver, which said process consists in, first, finely comminuting the 
ore; second, roasting the same in an oxidizing atmosphere; thirdly, leaching 
such roasted ore with water containing ferrous sulphate; fourthly, leaching such 
once leached ore with an aqueous solution of ferrous and ferric sulphates; fifthly , 
leaching such twice leached ore with water containing ferrous sulphate; and sixthly , 
removing iron from the zinc sulphate solution obtained by the first and second 
of the said teachings by mixing such solutions together and heating them. 

516016 March 6, 189 4. W. R. INGALLS and F. WYATT. Treatment of ores 
of zinc. The process of treating ores of zinc, which consists, first, in subjecting 
the ore to an oxidizing roasting; second, lixiviating the roasted ore with water 
and sulphuric acid; third, separating one-fourth of the zinc-sulphate solution 
thereby formed from the rest and precipitating the zinc from said separated por- 
tion by means of a sulphide of an alkaline base; fourth, evaporating the remainder 
of the zinc-sulphate solution to dryness and mixing the precipitated sulphide 
therewith; and lastly, heating the mixture in a suitable furnace whereby sul- 
phurous anhydride gas is evolved. 

518890 April 24, 1894. L. KLOZ. Process of extracting zinc from ores. The 
process of treating zinc ores, which consists, first, in the preparation of a concen- 
trated solution of sulphurous acid; second, in leaching the ores or furnace products 


with this solution to form a concentrated zinc sulphite solution free from sulphates; 
and third, scattering this solution by steam to dispel the sulphurous acid and 
precipitate the zinc sulphite. 

527473 October 16, 1894. P. ARGALL. Cyanide and chlorination process for 
treating gold- or silver-bearing ores. In the process of preparing gold- and silver- 
bearing ores for the extraction of the precious metals, the improvement consist- 
ing in separating the slime from the granulated ore, preventing the forming of 
acid in the slime by mixing lime therewith, and then forming the mixture into 
lumps for burning. 

541374 June 18, 1895. E. B. MIERISCH. Process of extracting gold and silver 
from their ores. The process of extracting gold and silver from oxidated or roasted 
ores, which consists in mixing the ground ores with sodium hydrate, mixed with 
a corresponding quantity of calcium hydrate, then subjecting the mixture to the 
action of chlorine, whereby the ores are acted upon by chlorates, and hydrochlorites 
formed "in statu nascendi," and then leaching the lye with a concentrated sodium- 
chloride solution, the deterioration of which is prevented by the addition of the 
calcium hydrate to the sodium hydrate. 

541447 June 18, 1895. H. F. WATTS and A. COAN. Process of reducing 
zinc slimes. The process of treating zinc slimes containing the precious metals, 
which consists in first treating the same with dilute sulphuric acid for the pur- 
pose of removing metallic zinc, washing the residue to remove the soluble salts 
and the remaining acid, and boiling the residue thus formed with concentrated 
sulphuric acid to dissolve the cyanide of zinc and the other salts thereof which 
are insoluble in the dilute acid. 

541659 June 25, 1895. J. J. CROOKE. Process of and apparatus for extracting 
silver from its ores. The process of extracting silver from its ores, which con- 
sists in roasting the ores with chloride of sodium, treating the roasted mass with 
a, hot aqueous solution containing chloride of sodium, nitrate of copper, and sul- 
phuric acid, and recovering the silver from the solution. 

544499 August 13, 1895. H. BREWER. Process of utilizing waste lye. The 
process of treating zinciferous or cupriferous lyes resulting from the lixiviation 
of chlorinated roasted ores, which consists in chemically extracting the metals 
in the lye, except the zinc, removing the sodium chloride by concentration of the 
lye, extracting the zinc and chlorine from the remaining lye electrolytically, and 
effecting the chemical extraction in such manner that the final lye will consist 
essentially of a solution of calcium chloride. 

544612 August 13, 1895. A. CROSSLEY. Process of manufacturing zinc. The 
process for the manufacture of zinc oxide, which consists in adding sulphuric acid 
to the metallic ores or compounds, heating the mixture and converting the lead 
present to an insoluble salt, and depositing any silver or gold present, then diluting 
with water and converting the other metals present to soluble salts, filtering off 
the clear liquor, then treating the clear acid liquor filtered off with an alkaline, precipitating the copper as copper sulphide, then filtering the liquor 
from the precipitate, treating with an alkali until neutral, passing chlorine into 
it until all manganese and iron present form manganic and ferric oxides, which 
are thrown down by a slight excess of alkali, adding an excess of alkali to bring 
the zinc oxide into solution, and then precipitating the zinc oxide, and filtering 
off the liquor therefrom. 

547587 October 8, 1895. C. V. PETRAEUS. Method of extracting zinc from 
complex ores. The method of separating zinc from complex ores where it is found 
as a sulphate or sulphite, which consists in crushing the ore, roasting it, dissolving 
out the soluble zinc salts in water, adding a solution of sulphuric acid to dissolve 
out any zinc oxide, introducing live steam to the mixture of ore and solvents to 
thoroughly mix and heat them, separating the solution of sulphate of zinc from 
the insoluble parts of t'.e ore, adding chloride of calcium to the solution to con- 
vert the zinc into a chloride, separating the solution of zinc chloride from the pre- 
cipitated calcium sulphate and finally adding quicklime to the solution of zinc 
chloride to precipitate the zinc as zinc oxide. 

556690 March 17, 1896. G. O. PEARCE. Process of extracting gold from 
solutions. The process of recovering gold and platinum metals from aqueous 


solutions of these metals, which consists in passing said solutions through a mass 
of vegetable carbon having associated with it sulphate of iron, oxalic acid, and 
tartaric acid. 

559614 May 5, 1896. G. A. SCHROTER. Extraction of precious metals. The 
process of extracting precious metals, particularly silver, from ores and metal- 
lurgical products, which consists in leaching the crushed and chloridized ore with 
a concentrated solution of brine to which has been added a small per cent (one- 
half to 4 per cent, approximately) of a soluble salt of copper. 

561544 June 2, 1896. F. P. DEWEY. Process of treating sulphides. The 
process of treating mixtures containing sulphides of silver and copper, which con- 
sists in heating the mixture with strong sulphuric acid, adding water, adding more 
mixed sulphides, separating the solution of sulphate of copper from the residue 
containing the sulphide of silver, and heating the sulphide of silver with strong 
sulphuric acid to convert it into sulphate. 

561571 June 9, 1896. F. P. DEWEY. Process of treating mixtures containing 
sulphides. The process of treating mixtures containing sulphides of silver and 
copper, which consists in heating them to a temperature at which the sulphur 
is oxidized, in an excess of sulphuric acid sufficient to convert the sulphides of 
silver and copper into sulphates, and bring the sulphate of silver into solution 
outside of the mass of material treated, thereby oxidizing the sulphur, converting 
the sulphides into sulphates, and bringing the sulphate of silver into solution in 
the acid outside of the mass of material acted upon. 

571369 November 17, 1896. B. HUNT. Process of refining gold and silver 
bullion. The process of refining bullion slimes by first roasting the slimes to decom- 
pose all cyanogen compounds and carbonaceous matters and then treating the 
roasted slimes with nitric acid. 

586159 July 13, 1897. H. BREWER. Process of treating zinc sulphide ores. 
In a process of treating zinciferous sulphate lyes resulting from the lixiviation 
of chlorinated roasted zinc sulphide ores, adding sodium chloride to such lye to 
saturation or in excess, and crystallizing out the resulting sodium sulphate (Glauber 
salt) by refrigeration as a by-product. 

587128 July 27, 1897. E. F. TURNER. Process of treating argentiferous sul- 
phide ores. In a process for the extraction of the metal of compound sulphide 
ores, disintegrating and decomposing the latter by the combined action of aqueous 
and gaseous hydrochloric acid, neutralizing the acid gases evolved whereby sul- 
phureted hydiogen is obtained, heating the disintegrated ore by means of such 
sulphureted hydrogen, collecting the sulphur dioxide resulting from the combus- 
tion, bringing this gas into contact with sodium chloride in presence of heat, whereby 
hydrochloric acid gas and sodium sulphate are obtained, and utilizing the former 
in the process of disintegration. 

588476 August 17, 1897. H. A. RHODES. Process of separating gold and 
silver or other precious metals from their ores. In chemical processes for the separa- 
tion of gold or other precious metals from their ores, slimes, or compounds, the 
method of preparing the ores by adding thereto a self-hardening, binding mate- 
rial and forming a porous and rigid mass of the compound whereby the precious 
metals contained therein are freely acted upon by the solvent. 

589959 September 14, 1897. J. J. CROOKE. Process of treating copper sul- 
phides. The process of recovering silver or gold and extracting copper in a metallic 
condition from copper sulphides associated with iron sulphides, which consists 
in roasting the pulverized sulphides with sodium chloride at a low heat, leaching 
the roasted mass with a solution whereby the iron sulphides are largely converted 
into oxides and the silver and gold are dissolved by and removed with the solu- 
tion, recovering the silver and gold from the solution, roasting the residuum or 
tailings, fluxing the rcasted tailings with silica and pulverized carbon, gradually 
melting the roasted and fluxed charge to convert the oxide of iron into metallic 
iron and desulphurize the copper sulphides to liberate metallic copper and form 
an iron silicate slag, removing the slag from the melted copper, adding a small 
per centum of silica to convert any remaining iron oxide or metallic iron into an 
iron silicate slag, and removing this slag from the copper. 


602295 April 12, 1898. E. A. ASHCROFT. Treating solutions or ores contain- 
ing zinc for recovering zinc as oxides. The process of treating neutral zinc solu- 
tions for the production of zinc oxide, which consists in first converting the neutral 
zinc salt into basic zinc salt by the addition of zinc oxide and then intimately \/ 
mixing with said basic zinc salt, carbon in approximately the proportion of one- ' 
twentieth of the weight of the zinc to be recovered, and heating the mixture to 
a temperature approximately the melting-point of aluminum. 

623154 April 18, 1899. H. HOWARD. Extraction of zinc and copper from 
ores. The process of extracting zinc and copper from ore or residue, which con- 
sists in treating the same with aqua ammonia and ammonium sulphate ; separating 
the copper from the resulting solution; adding sufficient soda to combine with 
all of the sulphuric oxide present and form sulphate of soda, and evaporating the 
solution to drive off ammonia, the latter being collected in water; and treating 
the residue with water to dissolve out the sulphate of soda, the zinc oxide remaining. 

624000 May 2, 1899. J. DURIE. Method of reducing metallic sulphides. In the 
process of causing the solution of metallic sulphides containing lead, subjecting the 
sulphide ore to a solution of sulphuric acid and a nitrate of an alkali metal at a tem- 
perature of about 212 Fahrenheit, washing and filtering the lead sulphate obtained 
therefrom, dissolving the said sulphate, precipitating by carbon dioxide, wash- 
ing, and drying the precipitated hydrated carbonate of lead, and recovenng the 

625433 May 23, 1899. M. BODY. Process of treating sulphureted ores. In 
the process of treating sulphureted ores of a complex nature, comminuting and I 
melting the ore in presence of an alkaline salt and carbon, whereby alkaline poly- I 
sulphides soluble in water are formed, plunging the melted mass into water, whereby 
a magnetic precipitate is formed and the polysulphides dissolved in the water, 
separating the solution from the precipitate, subjecting the same to the action 
of air and sulphurous-acid gas forced thereinto, whereby monosulp hides of iron, 
together with the precious metals, are precipitated, maintaining the alkalinity 
of the solution during the operation of precipitation by addition of an alkaline 
substance, as lime, separating the solution from the monosulphide-of-iron pre- 
cipitate, extracting from the latter the copper and then the precious meatl, and 
separating the arsenic and antimony from the solution by precipitation 

627024 June 13, 1899. R. THRELFALL. Method of treating flue dust and 
fume obtained from sulphide ores. In the treatment of flue dust and fume from 
sulphide ores, the separation of the zinc from the lead constituents by leaching 
out the former by means of a solution of alkali metal hydrogen sulphate, 

630951 August 15, 1899. L. VANINO. Wet process of extracting silver from 
its haloid salts. The wet process of extracting silver from its insoluble haloid 
salts, which consists in mixing said haloid salts with a watering solution of alka- ** 
line agents, and adding formic aldehyde in the cold. 

635056 October 17, 1899. D. O'KEEFE. Process of treating ore. The process 
of treating ore, consisting of roasting the same while being agitated, for the pui- ^ 
pose of mechanical disintegration, subjecting the ore to hydrogen gas under pres- 
sure, afterwards to chlorine gas, and then leaching the same with hot salt water. 

635695 October 24, 1899. C. MARTIN. Process of chemically preparing and 
treating rebellious ores. The process of effecting the separation of gold, silver, 
tin, lead, and platinum, in pulverized rebellious ore containing arsenic and anti- 
mony, which consists in effecting sulphurization and disintegration of the said 
ore, producing a sulphide solution of the metals in said ore, and thereupon pre- 
cipitating the dissolved metallic compounds other than arsenic and antimony 
by mingling the same with an oxide of an alkali earth metal. 

635793 October 31, 1899. F. W. MARTINO and F. STUBBS. Process of treat- 
ing ores containing pr^ious metals. The treatment of ores or tailings containing 
the precious metals by finely dividing the ore, mixing it with calcium carbide, ^ 
and moistening the mixture with water. 

644770 March 6, 1900. R. W. KENNEDY. Solvent for leaching ores. A 
solvent for leaching ores, comprising sodium thiosulphate, ammonium carbonate, 
copper sulphate, and potassium cyanide in water. 


647989 April 24, 1900. T. RYAN, Jr., and N HUGHES Process of extracting 
vine from substances containing same. The process of extracting zinc from sub- 
stances containing the same, consisting in subjecting the raw material to the action 
of a solution of a caustic alkali, precipitating any lead present by galvanic action, 
securing the removal of organic matters and iron, manganese, and silicon by the 
addition of caustic lime and bleaching-powder, and finally precipitating the dis- 
solved zinc in the form of zinc oxide or zinc hydroxide by decaustifying the solu- 
tion by the addition of an acid. 

648354 April 24, WOO. C. G. COLLINS. Process of extracting metals from 
their ores. The process of extracting metals from their ores, consisting in dis- 
solving out or extracting the metal from the powdered ore by means of a solution 
of ammonium salt in the presence of an alkali base capable of decomposing the 
ammonium salt, and then precipitating the metal by the addition of a solution 
of an alkali metal. 

652072 June 19, 1900. G. DE BECHI. Treatment of ore. The method of 
treating complex ores, consisting in subjecting the ore to a chloridizing roasting, 
condensing the vapors and gases evolved, treating the roasted ore and the acidu- 
lated water containing the condensed vapors and gases with calcium chloride 
to precipitate soluble sulphates and sulphuric acid as insoluble calcium sulphate, 
then lixiviating the ore with the acidulated water to obtain a solution of zinc and 
copper salts and fractionally precipitating zinc and copper from the said solution 
as hydrated oxides by successive additions of lime. 

652849 July 3, 1900. S. H. JOHNSON and H. L. SULMAN. Process of extract- 
ing metals from ores or slimes. The method of treating pressed slime cakes con- 
taining residual water, which consists in displacing the residual water with an 
equal volume of a solvent solution, mixing the cakes with a further quantity of 
solvent solution, removing the metal-bearing solvent solution by pressure, dis- 
placing the remaining portion of such metal-bearing solution with water and extract- 
ing the metal from said mteal-bearing solution, whereby all the operations may be 
performed with an approximately constant volume of the solvent solution. 

653414 July 10, 1900. E. FINK. Process of extracting copper or other metals 
from tailings or ores of such metals. The process of extracting copper and other 
metals from tailings or ores of such metals, which consists in subjecting the tail- 
ings or ore to the action of a solution containing sulphuric acid and to the action 
of an oxide or oxides of nitrogen in the presence of air or oxygen under pressure, 
whereby the metal is oxidized and dissolved and the oxide or oxides of nitrogen 
are converted alternately into a lower and a higher oxide or oxides, and finally 
separating the solution from the earthy matter of the tailings or ore and sepa- 
rating the metal from the solution. 

654804 July 31, 1900. G. RIGG. Process of obtaining oxide and carbonate 
of zinc from materials containing zinc. The process of producing oxide of zinc and 
carbonate of zinc from zinciferous material, which consists in leaching the zincifer- 
ous material with a solution of ammonia and carbon dioxide wherein the carbon 
dioxide is in such proportion to the ammonia as to impart to the latter an approxi- 
mately maximum zinc dissolving capacity. 

656497 August 21, 1900. G. DE BECHI. Process of treating zinc-bearing com- 
plex ores for recovery of zinc or other metals therefrom. The method of treating com- 
plex zinc ores for the recovery therefrom of copper, zinc, and lead, consisting in 
separately roasting the ore and an alkali chloride in the presence of air and steam, 
conveying the sulphurous and sulphuric vapors thus derived from the ore over 
and in contact with the said chloride during the roasting: to obtain hydrochloric 
acid fumes, condensing the acid fumes, lixiviating the roasted ore with the acid 
liquor thus obtained to produce a solution of metallic chlorides, and successively 
precipitating the metals of the metallic chlorides as hydrates by successive addi- 
tions of alkali. 

656544 August 21, 1900. H. HIRSCHING. Process of treating gold and silver 
ores. The process of treating copper ores, which consists in adding the com- 
mintued ore gradually under agitation to an ammoniated solution, and then adding 
a diluting liquid to the mixture to obtain a highly concentrated copper solution. 


657955 September 18, 1900. H. PETERSEN. Process of enriching metallic 
sulphides. The process of enriching metallic sulphides, which are mixed with 
carbonates of the alkali earth metals, consisting hi dissolving out the carbonates 
with an aqueous solution of sulphurous acid. 

659338 October 9, 1900. C. G. COLLINS. Process of extracting zinc and cop- 
per from their ores. The process of treating ores 'of copper and zinc, which con- 
sists in immersing the comminuted ore in a solution containing sodium sulphate 
and bisulphate (niter cake), removing the depleted ore and extracting the metal 
therefrom by electrolytic action, adding more comminuted ore to the remaining 
solution, and repeating the operation. 

659339 October 9, 1900. C. G. COLLINS. Process of extracting copper and 
zinc from their ores. The process of treating ores of copper and zinc containing 
other metals soluble in any excess of solution which may be employed above that 
required to dissolve the copper and zinc contained therein, which consists in intro- 
ducing the comminuted ore into a solution of sodium sulphate containing hydro- 
chloric and sulphuric acid (salt-cake solution) not exceeding 5 Baume, and sub- 
sequently recovering these metals from the solution. 

. 659670 October 16, 1900. C. J. HEAD and R. C. WILD. Method of treating 
telluride ores. A process for the extraction of tellurium from telluride aurifer- 
ous ores and the preparation thereby of said ores or the better extraction of the 
precious metal therefrom, consisting of a lixiviation and digestion of the said ores 
in a solution containing about 5 per cent, of caustic potash or soda for a lengthened 
period of fcwo to six hours, the withdrawal of the solution after such digestion 
from the said ores, and the recovery of the tellurium from the solution. 

660013 October 16, 1900. C. J HEAD and R. C. WILD. Method of treating 
telluride ores. A process for the extraction of tellurium from telluride auriferous 
ores and the preparation thereby of said ores for the better extraction of the precious 
metal therefrom, consisting of a lixiviation and digestion of the said ores in a solu- 
tion containing about 5 per cent, of carbonate of sodium or potassium for a lengthened 
period of two to six hours, the withdrawal of the filtrate, and the recovery of the 
tellurium from the solution. 

663759 December 11, 1900. C. HOEPFNER. Process of producing solutions 
of zinc chloride. The process, which consists in reacting upon an oxide or insoluble 
salt of zinc in presence of water with sulphurous acid to form soluble zinc bisulphite 
converting the bisulphite into a monosulphite by suitable reagents, mixing there- 
with its equivalent of sodium or potassium chloride and exposing the mixture to 
heat and air in the presence of a contact substance, such as oxide of iron, in order 
to convert the monosulphite into a sulphate, separating the zinc chloride from 
the solution and mixing therewith a sufficient quantity of an aqueous solution 
of sodium chloride to dissolve the zinc chloride and leave the alkali-metal sulphate 
practically undissolved. 

678210 July 9, 1901. J. W. WORSEY. Process of treating complex ores. 
Process for the treatment of complex sulphide ores, comprising, first, the reduc- 
tion of the combined sulphur below 15 per cent, by calcination; secondly, finely 
powdering the calcined ore; thirdly, adding sodium nitrate; fourthly, boiling 
the mixed ore and nitrate in dilute sulphuric acid; fifthly, roasting the semisolid 
mass in a closed furnace; sixthly, dissolving out zinc copper and other soluble salts 
from the said mass by weak sodium-sulphate solution; seventhly, removing any 
copper from the solution; eighthly, precipitating the zinc and other metals from 
the solution; and, ninthly, separating the zinc. 

679215 July 23, 1901. H. C. BULL. Method of extracting gold from sea-water. 
The method of extracting gold from sea-water, which consists in mixing with a 
quantity of sea-water a proportion of milk of lime to react upon the iodide of gold 
contained in the sea-water to form iodide of calcium and to liberate the gold, then 
allowing the sludge formed by the reaction to settle, then drawing off the water 
.and then collecting the sludge and treating it to extract the metallic gold therefrom. 

683325 September 24, 1901. H. J. PHILLIPS. Extraction of precious metals 
from their ores. The method of extracting precious metals from refractory sul- 
phide or telluride ores without roasting, which consists in subjecting the ore with- 


out roasting and in the form of a powder, under heat and pressure, to the action 
of alkaline polysulphides in solution of such weakness that same will have a selec- 
tive action, namely, will dissolve the elements which are combined with the gold, 
and for which the polysulphides have a greater affinity than for gold, without 
dissolving the gold itself, which latter is thus dissociated and can then be recovered 
by any known suitable process for recovering free gold. 

684578 October 15, 1901. C. W. MERRILL. Precipitant for recovering metals 
from solutions. The combination with a metal capable of precipitating other 
metals from cyanide solutions, if a gritty, inert, non-metallic material, to increase 
the surface exposed per unit of weight of the precipitating metals. 

689835 December 24, 1901. G. H. WATERBURY. Process of extracting copper 
from ores. The process of precipitating copper in solution, consisting in placing 
the solution in a tank or receptacle containing pieces of iron small enough to allow 
the solution to pass readily therethrough, and introducing hot air under pressure 
into the solution. 

692008 January 28, 1902. O. FROLICH, M. HUTH, and A. EDELMANN. Sepa- 
rating process for ores. In the art of separating metals from ores containing iron 
among- a plurality of metals existing therein in a combined form, the process, 
which consists in heating the ore to a temperature below the decomposition tem- 
perature of the sulphate of the metal to be sulphated, but above the decomposing 
temperature of the sulphate of any other metal existing in the ore, and then pass- 
ing over it a gas mixture containing sulphur dioxide and oxygen. 

693148 February 11, 1902. E. B. PARNELL. Process of treating ores. In' the 
treatment of refractory ores, the process, which consists in subjecting them to 
the action of chromic acid and then roasting them. 

695306 March 11, 1902. M. M. HAFF. Separation of the constituents of com- 
plex sulphide ores. The process, which consists in heating mixed sulphides of zinc 
and lead with sulphate of an alkali metal, treating the resultant mass with a dis- 
solving agent to dissolve the zinc sulphate and alkali -metal sulphate, while leaving 
the lead sulphate undissolved, and adding barium hydrate to the mixed solu- 
tion of zinc sulphate and alkali-metal sulphate to precipitate zinc hydrate and 
barium sulphate. 

699326 May 6, 1902. T. A. IRVINE. Extraction of copper by the wet method. 
A process for the extraction of copper, consisting in the treatment of the ore within 
a mixed solution of chloride of sodium and sulphuric acid, in which solution there 
is an excess by weight of the chloride of sodium in respect to the sulphuric acid. 

700311 May 20, 1902. F. ELLERHAUSEN. Treatment of complex and refrac- 
tory ores. The process of treating complex and refractory ores containing lead, 
silver, and zinc, which consists in smelting the raw ores, churning the fumes and 
gases with water to condense and mix them with water, settling out the lead, sil- 
ver, and part of the zinc compounds from the resulting liquor, as a sludge, sepa- 
rating and drying the sludge and fusing the sludge with caustic alkali, thereby 
precipitating the lead in metallic form. 

702047 June 10, 1902. C. G. COLLINS. Process of rendering metallic sul- 
phides soluble. The process of rendering metallic sulphides soluble, consisting 
m drenching the crushed sulphide ore with aqueous ammonia, draining off the 
excess of aqueous ammonia, treating the ore thus moistened to an excess of oxygen, 
leaching the ore, and repeating the operation until the metal is all extracted from 
the pulp. 

702153 June 10, 1902. J. P. VAN DER PLOEG. Treatment of ores and mate- 
rials containing antimony. The method of extracting antimony from ores, mate- 
rials, or residues containing it, consisting in finely pulverizing the material, mixing 
it with a suitable quantity of powdered quicklime, and then mixing with it an 
adequate quantity of sulphide of an alkali-earth metal and water, so as to form 
a solution of the lower and most soluble double sulphides as being the best elec- 
trolytes, without the use of artificial heat or application of pressure. 


702244. June 10, 1902. A. J. POLMETEER. Precipitant for treatment of cop- 
per-water. The precipitant for copper-water, containing in solution a sulphide 
and an excess of alkali. 

702582 June 17, 1902. J. W. NEILL and J. H. BURFEIND. Process of recwer- 
ing metals from ores. The improvement in treating copper or other ores, consisting 
in agitating a charge of pulp containing the ore by gas from* roasting furnaces v , 
charged with material suitable for producing sulphurous-acid gas, separating the Vy' 
resultant solution, precipitating the metal from the solution thereby releasing;'/^ 
gas and employing the sulphurous-acid gas released by the precipitating process 
to enrich the gas derived from the furnace and used in leaching a charge of ore. 

704640 July -15, 1902. C. HOEPFNER. Process of extracting copper and 
nickel from sulphide compounds. The process, which consists in oxidizing roast- 
ing copper and nickel sulphide ores or mattes, leaching the sulphate of copper 
formed, converting this into cupric chloride and then into cuprous chloride, dis- 
solving the nickel salts in the residue by said cuprous chloride, precipitating cup- 
rous chloride from the solutions formed and returning the resulting solution con- 
taining some cuprous chloride into the cycle of operations. 

704641 July 15, 1902. C. HOEPFNER. Process of extracting zinc or other- 
metals from their ores. The process which consists in reacting on a material con- 
taining an oxygen compound of metals insoluble in water and whose chlorides- 
are soluble in a solution of alkali metal chloride, with sulphurous acid and an aque- 
ous solution of alkali metal chloride, whereby a solution is formed containing a 
chloride of a metal. 

706302 August 5, 1902. L. B. DARLING. Means for extracting precious 
metals from ores. In a gold-extracting plant provided with a substantially flat 
treating floor of non-absorbent material, a series of longitudinally extending chan- 
nels formed therein, a transverse groove or end launder in direct communication 
with said channels, fixed screens or strainers covering the top of said channels and 
launder, side launders or ducts, and valved connections interposed between and 
uniting the said end and side launders. 

707107 August 19, 1902. J. HERMAN. Process of treating ores. The process 
which consists in roasting sulphide of copper ore at a low heat to form sulphates 
of the copper and some of the iron present, and produce a large percentage of fer- 
rous sulphate, leaching the roasted ore, precipitating the metallic copper, and 
adding salt to the leaching solution before or after the precipitation of the metallic 
copper, whereby the ferrous salts in the solution are converted to the chloride f 
and a solution having an excess of salt is produced, and the said solution is adapted 
to dissolve copper and silver out of carbonate and oxide ores. 

707506 August 19, 1902. E. FERRARIS. Method of treating mixed sulphide 
ores. The process of decomposing mixed sulphide ores by means of concentrated 
sulphuric acid without the aid of extraneous heat. 

709037 September 16, 1902. W. PETHYBRIDGE. Treatment of telluride gold 
ores. In the decomposition of ores containing telluride of gold, the process of 
reducing the ore to a finely divided state and then exposing the ore to the action 
of a solution of ferric chloride alone to attack the tellurium. 

715023 December 2, 1902. J. C. CLANCY and L. W. MARSLAND. Process 
of treating zinc sulphide ores. In extracting metals from zinciferous sulphide ores, 
roasting pulverized ores with the addition or admixture of lead sulphate obtained 
from a source external to the ore being treated in quantity proportional to the 
quantity of zinc the ore contains. 

715771 December 16, 1902. F. ELLERHAUSEN and R. W. WESTERN. Treat- 
ment of zinc ores. The process for the treatment of zinc ores and other zinciferous 
matter, consisting in calcining where necessary, wetting with a dilute solution 
of ammonium sulphate, adding sulphuric acid, washing with ammonium sulphate , 
and precipitating with aqueous ammonia and heating the precipitate. 

715804 December 16, 1902. H. E. HOWARD and G. HADLEY. Treatment of 
spent acid from galvanizing works. The treatment of spent acid from galvanizing 
works by adding zinc thereto, separating the solution from the precipitate, treat- 


ing with bleaching powder to transform the ferrous salts into ferric salts, then 
adding alkali to precipitate the iron present as ferric hydrate, and subsequently 
more alkali for the precipitation of the zinc salts. 

71684? December 23, 1902. F. W. MARTINO. Treatment of ores containing 
precious metals. The process of separating gold from ores containing tellurium, 
r selenium, sulphur, arsenic, antimony, tin, phosphorus, or the like, consisting in 
grinding the mixture, heating it with powdered barium sulphocarbide in a reduc- 
ing (muffle) furnace, dissolving out the soluble sulphides thus formed, treating 
the solid residue with a gold solvent, and precipitating the gold therefrom by the 
employment of barium sulphocarbide. 

717299 -December 30, 1902. G. C. STONE. Extraction of zinc and lead from 
sulphide ores. The method of separating zinc and lead from sulphide ores, which 
consists in smelting the sulphides, oxidizing the volatile constituents at their exit 
from the smelting furnace, cooling the resulting fumes and products of combus- 
tion to a temperature not exceeding 180 F., and passing them into contact with 
a solvent which will dissolve out one of the metals and not the other. 

717565 January 6, 1903. A. VON GERNET. Process of extracting copper 
from its ores. The process of extracting copper from its ore, which consists in 
^X. slowly passing the ore in the form of pulp through a current of sulphurous acid, 
passed in a direction opposite to that of the travel of the pulp. 

7 17 86 4 January 6, 1903. J. T. JONES. Method of treating ores. The process 
of mixing with ore, to be treated, a leaching fluid, which consists in confining the 
mass of ore in a vessel with a body of leaching fluid of lesser specific gravity super- 
imposed upon it, carrying portions of the ore upward in said vessel and releasing 
it above the body of leaching fluid, to precipitate it through said body and simul- 
taneously convey portions of the leaching fluid below the surface of the mass of 
ore and releasing it and permitting it to rise through the same. 

718099 January 13, 1903. S. C. C. CURRIE. Method of reducing ores. The 
step in the art of treating pulverized ores containing precious metals, which con- 
sists in subjecting the ore, in a closed vessel, to the action of hot air at a tempera- 
ture which reduces some of the salts in the ore from an insoluble to a soluble 
condition in water, , then washing ^ away the soluble salts with water and then 
repeating the step with air at a higher temperature. 

719132 January 27, 1903. W. PAYNE, J. H. GILLIES, and A. GONDOLF. 
Process of treating copper^ ores. The process of treating copper ores, consisting 
in first roasting to an oxide, next saturating the same with a solution of ferrous 
sulphate or sulphate and chloride, next roasting again and meanwhile adding a 
small percentage of iron sulphide or sulphur, according to the percentage of cop- 
per present, and finally leaching the hqt ore. 

719757 February 3, 1903. S. C. C. CURRIE. Process of treating ores con- 
Jy taining precious metals. The method of treating ore, which consists in heating 
the raw pulverized ore in contact with steam, and plunging the heated ore into 
an aqueous alkaline solution. 

723787 March 24, 1903. S. TRIVICK. Process of extracting metals from ores. 
A process for evolving nascent chlorine and effecting the chlorination of metallic 
substances in order that they may be extracted from a metalliferous mass by 
rendering them solvent, consisting in adding to the mass a mixture in definite 
proportions of two substances, one being dry chloride of lime and the other ferric 
sulphate, the proportions being such as to result in the formation of ferric hypo- 
chlorite and ferric chloride which will evolve nascent chlorine. 

723949 March 31, 1903. G. D. VAN ARSDALE. Process of separating copper 
from ores. The process of extracting copper from ores, or products containing 
copper, which consists in separating copper from cupric-sulphate solutions, with 
or without ferrous or other suitable sulphate, and of simultaneously producing 
free sulphuric acid, by adding to such solutions sulphur dioxide and heating with 
or without pressure, whereby copper or copper compounds are thrown down in 
the solid form to be subsequently treated, and free sulphuric acid is formed, and 
of adding the acid liquors thus obtained, after separation from the copper pre- 
cipitate, to copper ores, whereby the copper contained in them is dissolved and 


the original solution regenerated and the process repeated and thus made con- 

724414 March 31, 1903. G. H. WATERBURY. Copper leaching process. The 
copper leaching process, consisting in placing the suitably pulverized ore in a leach- 
ing-tank, adding water, acid, common salt, and oxide of manganese in suitable 
quantities, heating the mass by the introduction of steam to a suitable temperature, 
and finally subjecting the pulp to agitation during a suitable period. 

725257 April 14, 1903. T. B. JOSEPH. Gold extraction process. The process 
of extracting precious metals from ore containing the same, when in a suitable 
condition, which consists in subjecting the said ore to a leaching action of a solu- 
tion of water, cyanide of potassium, hydrate of calcium, carbon dioxide, and bio- 
mine, and subsequently precipitating the precious metals from the solution. 

725548 April 14, 1903. H. R. ELLIS. Process of extracting copper from car- 
bonate and oxide ores. The process of extracting and recovering copper from its 
carbonate or oxide ores or from material carrying carbonates or oxides of copper,, 
which consists in subjecting the ore or other material in a crushed or powdered 
state to the action of a carbonate of soda or its described equivalents until the 
copper is dissolved and subsequently subjecting the charged solution to electrolytic 

726802 April 28, 1903. B. T. NICHOLS. Ore-treating process. The process 
for treating ore preparatory to leaching, consisting first in mixing the suitably 
pulverized ore with lime; second, applying water to the mixture and introducing 
steam whereby the pulp is agitated and kept at a suitable temperature until cer- 
tain impurities which retard leaching are freed; third, washing the pulp by the 
introduction of water and continued agitation; fourth, draining on the water 
as far as practicable; and, finally, drying the ore. 

729760 June 2, 1903. G. V. GUSMAN. Process of reducing and separating 
silver. The process of extracting and separating silver from its ores, which con- 
sists in subjecting roasted ores to the action of a preprovided aqueous solution 
of cupric chloride and cuprous chloride, passing the resulting solution through 
granulated metal, and removing and collecting the metallic silver from said metal. 

729819 June 2, 1903. J. F. WEBB. Apparatus for use in extracting metals 
from ores. A tank for use in extracting metals by chemical process from their 
ores, having a filter bottom and means for discharging air within the tank and 
downwardly upon the said bottom, whereby the said bottom is kept free frcm 
clogging and air is supplied to agitate the mass within the tank and supply oxygen 

734683 July 28, 1903. J. F. DUKE. Process of obtaining gold from sea-water. 
The process of obtaining gold from sea-water containing the same, which con- 
sists in precipitating the gold by carbonate of calcium. 

735098 August 4, 1903. C. HOEPFNER. Process of obtaining lead or other 
metals from ores or mattes. The process, which consists in leaching compounds 
containing lead and iron with a solution of cupric chloride containing a solvent 
of the chlorides of said metals, supplying oxygen to produce oxychloride of cop- 
per whereby the iron is precipitated, and precipitating the lead as a sulphite by 
means of a sulphite of zinc. 

735512 August 4, 1903. H. HIRSCHING. Treatment of ores containing gold r 
silver, copper, nickel, and zinc. The process for extracting gold, silver, copper, 
nickel, and zinc from substances containing the same, which consists in subject- 
ing said substances to the action of an acid, washing with water the substance 
thus treated, thereby forming solutions containing compounds of gold and base 
metals, and then subjecting said solutions to the action of ammonia for the pur- 
pose of precipitating the gold and recovering the base metals from the solution, 
separately, and also the ammonia. 

739011 September 15, 1903. F. LAIST. Process of treating ores. The method 
of generating hydrogen sulphide and precipitating copper, which consists in sub- 
j^cting an alkaline-earth sulphide in presence of water to the action of csrbcn 
d'ox'de, thereby generating hydrogen sulphide and precipitating the carbonate 
of the alkaline-earth metal, conducting said hydrogen sulphide into the presence 


of copper in solution, thereby precipitating copper sulphide and forming a sol- 
vent liquid, treating copper ores with said solvent liquid, and collecting said 
alkaline-earth carbonate and reconverting it into sulphide. 

740014 September 29, 1903. J. HERMAN. Process of treating ores. A process 
of extracting copper from ores, which consists in treating ore containing iron to 
produce ferrous chloride, utilizing the chloride and free acid to dissolve carbon- 
ates and oxides of copper, the free acid being adapted to neutralize interfering sub- 
stances and to attack the surface of the particles of copper oxide or carbonate, 
and regenerating the free acid by the electrolytic precipitation of copper. 

740372 September 29, 1903. C. ROGERS. Process of extracting zinc from sul- 
phide ores, etc. The process for the extraction and recovery of zinc from zinc 
containing sulphide ores or tailings, which consists in subjecting the same to a 
partial sulphatizing roast, discharging the same while hot into water, leaching 
the same with said water and with dilute sulphuric acid, subjecting the leached 
ores or tailings to a second sulphatizing roast, releaching the same with the lix- 
ivium from the former leaching, and repeating said operations until sufficient zinc 
and sulphur are removed. 

740701 October 6, 1903. A. M. G. SEBILLOT. Treatment of sulphide ores. A 
process for treating ores containing sulphur consisting of sulphating the ore in 
a closed vessel by the action of sulphuric acid upon the metallic sulphides at a 
temperature above its boiling-point and simultaneously recovering the sulphuric 
acid used, calcining the sulphated ore at a temperature of 700 Centigrade to dis- 
sociate the sulphate of iron to prevent dissolving of a too great quantity of sul- 
phate of iron in .the lixiviating liquors, and then lixiviating the calcined ore. 

748662 January 5, 1904. A. M. G. SEBILLOT. Process of treating copper 
ores. The process for extracting pure metals from mineral ores, consisting in 
treating the ores with sulphuric acid at the evaporating-point of the latter, with- 
out roasting, to form sulphates, condensing the surplus acid fumes, and lixiviating 
the sulphates in successively deeper baths under constant agitation, in a current 
flowing in direction opposite to the progress of the ores. 

749700 January 12, 1904. P- NAEF. Process of lixiviating ores. The method 
of lixiviating ores or other pulverulent materials, which consists in passing the 
ore downward in thinly divided layers through an ascending stream of leaching 
solution and at the same time passing a current of air or gas repeatedly through 
the ore layers in numerously divided jets, whereby the ore particles are agitated 
in the solution, and the same volume of gas acts successively as an agitating medium. 

752320 February 16, 1904. J. B. DE ALZUGARAY. Extraction of metals from 
complex ores. In the treatment of complex ores, such, for instance, as contain 
copper, lead, silver, and zinc in comparatively large quantities, the process of 
extracting the said metals selectively, which consists in leaching the ore with a 
solution composed of a mixture of a chloride of an alkali or earth-alkali metal 
with a chloride of a metal other than those of the alkali or earth-alkali series and 
an acid before calcination or roasting whereby the copper is obtained in solution 
then washing and drying the ore, roasting the partially disintegrated ore at a low 
temperature, extracting the metals from the roasted ore in form of salts by means 
of a second and weaker leaching solution having a character consonant with the 
nature of the salt it is desired to obtain, and recovering the metals in the usual 

754643 March 15, 1904- K. DANZIGER. Process of separating iron pyrites 
from zinc-blende. A process for separating iron pyrite from zinc-blende, which 
consists in exposing the zinc-blende to the action of air moisture and heat, and 
extracting the ferrous salt which has been formed by the oxidizing action by water. 

755871 March 29, 1904. T. A. HELM. Apparatus for treating ore. An 
apparatus for treating pulverized auriferous ores, comprising a rotatable cylin- 
drical tank, radially depending blades in the tank extending the length thereof, 
a circular brace-frame disposed between the inner ends of the radial blades, as 
an air pipe leading into the tank, faucets to draw off a liquid from the tank, and 
means to rotate the tank. 



108158 October 11, 1870. W. S. LAIGHTON. Improvement in apparatus for 
precipitating gold and silver from solutions. The invention consists in combining 
two vessels one to receive the solution to be precipitated and the other the pre- 
cipitant and connecting them by an automatic apparatus that shall deliver a 
certain quantity of the precipitant into the other vessel every time it is filled and 
provide for the discharging of the same, the quantity of the solution that receives 
the precipitant, measured out, being governed by a hydrometer or hydrometric 
float, which is used to operate the apparatus. 

213382 March 18, 1879. C. C. BITNER. Improvement in apparatus for obtain- 
ing metallic copper from its solution. The invention relates to a novel apparatus 
for obtaining metallic copper from its solution; and it consists in the employ- 
ment of a tank or vat having a horizontal perforated diaphragm, upon which is 
placed a quantity of iron. This tank is filled with a solution of copper, previously 
prepared from the roasted ore in the usual manner. Through the top of this 
tank a steam pipe passes and extends below the diaphragm, so that the solution 
is heated by this injected steam, and, by the motion which its action gives, the 
deposition of the copper is hastened. By means of peculiarly arranged slides 
the steam is admitted above the diaphragm through holes in the steam pipe to 
assist the process, if desired. 

234073 November 2, 1880. R. SCHULDER and E. H. RUSSELL. Ore-leacher. 
The invention consists of a circular frame supporting the filter and moving on a 
circular track above an inclined circular table; and it consists, further, of three 
stationary rollers, designed to elevate and depress the filter at certain points as 
it revolves, of a device for feeding the substance to be leached upon the filter, of 
a device for applying the leaching solvent, and of a precipitating tank to contain 
the solution passing through the filter. 

248768 October 25, 1881. J. F. N. MACAY. Filter. The invention relates to 
improved apparatus for use in effecting the operations of dissolving solids in liquids 
and producing chemical reactions, and of filtering or separating liquids from solids 
in chemical and metallurgical processes, in which a soluble substance or substances, 
mixed or combined with an insoluble substance or substances, is or are to be dis- 
solved separately or together, wholly or partially, in a given solvent or solvents, 
and the solution separated by filtration from the undissolved residue. 

In effecting the separation of liquid from solid matters by filtration it is of 
importance to keep the filtering surface from being clogged by the particles of 
solid matter, and to present a clear and unobstructed filtering surface for effecting 
the rapid separtaion of the liquid from the solid matters. In the apparatus of 
the invention this important condition is realized in a very effective manner, the 
construction and operation of the apparatus being as follows: 

Within a cylinder of wood or other material not chemically acted on by the 
materials treated or the reagents employed is inclosed an inner cylinder of hard 
wood, or of hard earthenware or stoneware or other material not chemically acted 
on by the materials treated or the reagents employed, this inner cylinder being 
perforated with holes and lined internally or externally, but preferably inter- 
nally, with asbestos cloth or other suitable filtering material. 

Between the inner and outer cylinder there is an annular space, and the inner 
cylinder is kept in place by longitudinal and circumferential partitions, the former 
of which divide ftie annular space into a number of distinct compartments each 
provided with a draw-off cock for running off the liquid when separated by fil- 
tration. This cylinder is capable of being rotated, and is provided with doors 
or manholes in one of the heads by which the matters to be treated may be intro- 
duced and the undissolved residue removed; and the cylinder is also provided 
with a tubular journal or journals for the introduction of steam, water, air, or 
other liquids or gases, under pressure or otherwise, which may be blown, forced, 
or drawn into the annular space for the purpose of keeping the filtering surface 


clear and of acting chemically or mechanically upon the contents of the cylinder. 
I place within the inner cylinder the ore or other matter to be treated (previously 
ground or otherwise reduced to a pulverulent state), together with the reagents 
.or solvents by which it is to be treated. By imparting rotary motion to the cylinder 
'(the draw-off cocks and manholes being closed) the solid matters are brought 
into intimate contact with the solvents or reagents, and by forcing steam, water, 
air, or other liquids or gases into the space between the ini ^r and outer cylinders, 
and thence through the filtering medium into the inner cylinder, any solid mat- 
ters that may adhere to the filtering surface are disengaged therefrom, whereby 
the said surface is kept clear, the solid matters are kept in suspension in the liquid, 
and chemical action, which the liquid or gaseous reagents may be capable of exert- 
ing on the said matters, takes place under the most favorable circumstances as 
regards the intimate mixture of the reagents with the matters and the large sur- 
faces exposed to their action. The annular space between the inner and outer 
cylinders being divided into compartments by longitudinal divisions, the liquid 
which passes through into it is carried round by the rotation of the cylinder and 
flows back into the inner cylinder, thus helping to keep the filtering surface clear 
and unobstructed. When the soluble substances are dissolved or chemically 
acted upon, and it is desired to separate the liquid from the solid matters, the 
draw-off cocks are opened, and then, by giving a slow rotary motion to the appara- 
tus, the liquid may be decanted off from the bulk of the solid matter and at the 
same time filtered from any such matters which it may hold in suspension by passing 
through the filtering medium. By this rotary decanting action a practically clear 
filtering surface, unobstructed by solid matter, is constantly presented for the 
liquid to pass through. 

251718 January 3, 1882. A. E. JONES. Apparatus for separating gold from 
quartz and rock tailings. The invention consists in the arrangement and applica- 
tion of a suitable fibrous material in combination with machinery, so that the 
fibrous material will unite or collect to itself the gold and carry and deposit the 
same to a place designated, where it may be collected and treated as desired in 
separating the precious metal from its sand and ore. Any fibrous matter that 
will form a pulp when mixed with water is used to coat a wire-cloth screen as in 
paper-making, and then entangle the fine gold in suspension in the water. 

301460 July 1, 1884. J- L . RUSSELL. Slime filter. The invention consists 
of a trough' containing at intervals within it a series of double filtering boxes 
covered with wire gauze and filled with charcoal, sponge, or any known filtering 
substance, and the claims cover the trough poised over filter sections provided 
with adjustable partitions, as well as the combination of a sand box, a sluice pro- 
vided with adjustable partitions, filters composed of frames and wire gauzes, and 

325835 September 8, 1885. H. C. and J. A. HENDERSON. Apparatus for con- 
centrating ores. The apparatus for concentrating ores, consisting of an outer 
tank, an inner tank provided with fabric ends, and a perforated feed-box hav- 
ing its lower end below the top edge of the tank, a space being left between the 
sides, ends, and bottom of the tanks whereby, when the water is received by the 
perforated feed-box, it will pass into the inner tank and slowly filter through 
the fabric ends thereof and flow over the top edge of the outer tank, the fabric 
ends preventing the formation of a current and causing the particles of ore to be 

366103 July 5, 1887. O. HOFMANN. Process of extracting silver from its ores by 
lixiviation. The invention relates to a certain improvement in the lixiviation process 
by which the ore, after having been subjected to a chloridizing roasting, is in- 
troduced in a series of troughs, first, together with water to dissolve the base- 
metal chlorides, and, sceond, together with the solution used in the ordinary 
lixiviation process to dissolve the silver. The ore and water are introduced either 
by means of a mixing-box or an agitator, and are allowed to flow in these troughs 
for some distance, and finally conveyed by them into settling-tanks. The water 
while running in the troughs dissolves the base-metal chlorides. In the settling- 
tanks the ore separates quickly from the liquid. The latter is drawn off and con- 
veyed to other tanks for the usual treatment. The ore sediment containing the 


silver is now sluiced or charged again in a similar series of troughs with a solution 
which has the property of dissolving chloride of silver, like hyposulphite of lime 
or soda, concentrated salt solution, Russell's "extra solution" (a compound of 
hyposulphite of lime or soda and bluestone), etc. By passing through this second 
series of troughs the silver chloride dissolves. Ore and solution run into tanks 
which are provided with filter bottoms and allowed to separate. The tailings 
settle to the bottom, while the clear solution, now containing the silver, is drawn 
off and conveyed into the precipitation-tanks for the usual treatment. 

370871 October 4, 1887. F. F. HUNT. Apparatus for agitating solutions in 
the leaching of metals from their ores. The invention relates to an improvement in 
apparatus for agitating the acid solutions formed in the leaching of copper and 
other ores; and the object of the same is to provide a form of rotary agitator in 
which the heavier portions of the charge cannot accumulate at the centre of the 
apparatus and escape the action of the agitating arms, which will also produce a 
more perfect agitation of the solutions than has heretofore been possible, and which 
will be more durable and economical to construct than the forms in present use. 

Heretofore the agitators used in leaching works have usually been made with 
flat bottoms and have been provided with stirring or agitating arms of conical 
shape at the base, arranged to rotate a slight distance above the bottom. In 
the invention this arrangement is reversed, and the agitating tank is constructed 
with a cone of small altitude placed apex upward in the centre of the bottom and 
covering a considerable portion thereof, and is provided with agitators, the arms 
of which are provided with concave shoes and are arranged to rotate in close prox- 
imity to the cone in the bottom of the tank. 

^1 26 '10 October 8, 1889. J. B. HANNAY. Apparatus for applying chlorine to 
the extraction of gold from ores. This invention relates to means of extracting from 
ores precious metals, especially gold, in the form of chloride solution. For this 
purpose an apparatus is employed which consists of a chlorinating vessel, a set 
of circulating pumps, a filter-press, and a chlorine pump, or sets of these, with 
suitable communicating pipes, cocks, and valves for operating in the following 
manner: Having reduced the ore to a fine powder, it is mixed with water or with 
chlorinated water to a condition of thin sludge, which can be pumped. Then charge 
the chlorinating vessel with this sludge and apply the pumps to cause its circula- 
tion therein, drawing from the upper part and discharging into the lower part, 
while chlorine gas is pumped into the vessel, preferably to a pressure considerably 
above that of the atmosphere. After circulation has gone on for some time, until 
the metal in the ore is mostly dissolved by the chlorine, the sludge is pumped by 
the circulating pumps into the filter-press, additional pressure being given, if re- 
quired, by using the chlorine pump to force air into the upper part of the chlorin- 
ating vessel. The liquid issuing from the filter-press containing in solution the 
metallic chloride is treated in any of the known ways for separating the metal 
and recovering the chlorine. In some cases the solution discharged from the filter- 
press may be used in a subsequent operation to form the sludge by its admixture 
with a fresh quantity of pulverized ore, and this may be done repeatedly, so as to 
obtain finally a filtered liquor rich in chloride. 

As it is advantageous to charge the chlorinating vessel with an excess of chlorine 
above that which enters into combination with the metals, the inventor prefers 
to collect such excess before discharging the sludge by blowing in a little steam 
to warm the sludge and allowing the free chlorine thus liberated to pass either 
into a gasometer or into another chlorinating vessel; or an exhaust-pump may be 
employed to draw off the free chlorine. 

When metals such as silver are present, having insoluble chlorides, the blocks 
which are taken from the filter-press, and which contain these chlorides, may be 
reduced to sludge, as before mentioned, and may be subjected to the same treat- 
ment with a suitable solvent instead of the chlorine. 

418138 -December 24, 1889. J. S. MACARTHUR. Metallurgical filter K metal- 
lurgical filtering apparatus for separating a precious metal from a solution containing 
said metals, consisting of a series of vessels, each of which has an inlet tube near 
its bottom, an outlet tube near its top, and a perforated false bottom above th3 
inlet tube, zinc sponges disposed in the several vessels, pipes connecting the inlet 


and outlet tubes of the several vessels, and a reservoir for supplying the solution 
to the first vessel of the series. 

425025 April 8, 1890. D. DENNES and T. K ROSE. Apparatus for leaching 
ores. In a leaching apparatus, a movable table, having a flange or wall projecting 
from its upper surface to form a receptacle for filtering material, the said receptacle 
being of, less diameter than the upper surface of the table, whereby a packing 
receiving ledge projects beyond the base of the said wall or flange, combined with 
the leaching cylinder, the lower end of which is constructed to receive said wall 
or flange, while the ledge abuts against said lower end of the cylinder. 

442262 December 9, 1890. S. TRIVICK. Apparatus for treating ores to obtain 
precious metals therefrom. This invention relates to improvements in apparatus 
forming a plant for treating roasted ground ores to obtain precious metals there- 
from, adapted for use in treating roasted ground ores of precious metals that have 
been roasted by any known or suitable method. 

The apparatus consists, essentially, of a vessel (preferably employing a pair 
at least of such vessels, so as to change from one to the other of the pair in working) 
having a porous bottom on which the ground-roasted ores rest; means of supply 
of leaching liquid controlled by valve; means of drawing off leached liquid, con- 
veyance thereof to, and means of stirring said liquid in a mixing chamber a filter 
vessel having a porous floor and means of pumping the filtered liquid to a reser- 
voir; means of evaporating the leaching liquor to recover the contained salts; 
also recovering the copper salts for reuse, and means of heating the leaching liquid, 
and also means of desiccating the product. 

The invention also consists in a furnace for roasting ores of precious metals, 
comprising, among other features, a chamber, coils of piping, a tank, reservoir, 
a force-pump, a system of heating pipes, leaching reservoir, tanks with porous 
floors, and a mixing vessel with rotating stirrers therein. 

449813 April 7, 1891. J. CRAGG. Apparatus for extracting gold or silver from 
ares. In an apparatus for extracting gold or other metals from their ores in solu- 
tion, a tower and a mixer, which consists of a trough having pipes to conduct the 
reagents in liquid solution, which enter the same from different sides and terminate 
out of alignment about centrally of the trough, combined with a hopper placed over 
the ends of the said pipes and an overflow plate leading to the said tower. 

456323 July 21, 1891. P. L. GIBBS. Ore-leaching machine. This invention 
has reference to ore-leaching machines in which a rotating annular series of 
ore receptacles pass successively under an ore vat containing the crushed ore in 
a solution to receive their respective contents or to be otherwise filled, and to 
discharge the filtrate during their transit into a suitably placed discharging con- 
duit or launder and at a predetermined point in their orbital movement and auto- 
matically discharge the residuum. 

The objects of this improvement are, first, to provide a suitably suspended 
vat to receive the ore in a solution, or dry or roasted ore, and adapted by suitable 
openings in the bottom thereof to optionally discharge said contents; second, 
to provide a series of leaching-vats to pass successively under said primary vat 
and respectively receive from the latter a proper quantity of its contents; third, 
to provide suitable mechanism for supporting and progressing said secondary vats; 
fourth, to provide a conduit or launder to receive and carry off the filtrate from 
said leaching or secondary vats; and, fifth, to afford facilities to automatically 
discharge the residuum from said leaching-vats preparatory to their refilling. 

463120 November 10, 1891. D. DENNES. Leaching-vat for separating precious 
metals from their ores. An ore-leaching apparatus consisting of a closed vat or 
separating vessel having a removable bottom carrying a filter-bed in its upper 
portion and an auxiliary chamber beneath, provided with a removable bottom and 
a filter-bed, and a suitable pipe connection between the separating vessel and 
said auxiliary chamber in its bottom. 

464672 -December 8, 1891. W. D. BOHM. Apparatus for separating gold 
and silver from ore. The inventor places the powdered or divided ore, or material 
to be treated for the obtainment of the gold or silver, or both, in a vessel or vat, 
or vessels or vats, and through it passes the leaching solution, preferably pre- 


viously heated. By means of a force-pump, the leaching solution is forced up 
through the ore and through a filter at the top. The solution and the precious 
metal which it now contains pass into a vessel in which it is agitated with a pre- 
cipitating agent. From this last-named vessel the solution is forced up by a force- 
pump through a vessel having a filtering arrangement, such as a porous diaphragm, 
at the top, so that the solid matter is retained thereby, the liquid passing off to 
be heated again and to be restrengthened by the addition of the necessary further 
quantity of leaching chemicals and passed back to the leaching vat or vats for 
reuse. The pressure under which the liquids are forced up through the leaching- 
vat and precipitant vessel should be at least eighteen pounds per square inch. 
At intervals the solid matter retained by the last-named filter vessel is passed into 
a filter-press or equivalent apparatus, whereby it is deprived of the greater part of 
its moisture. The ore which has been leached is then drained of all solution and 
washed free from the last traces thereof with water, preferably hot, and then can 
be washed out of the vat or vats with acidulated water, and passed over zinc or 
alloy of zinc with other suitable metal, so that hydrogen is evolved, which reduces 
any precious metal still remaining in the ore to the metallic state, or such state 
that it is taken up when the ore is afterwards passed over mercury for instance, 
over amalgamated copper. 

495385 April 11, 1893. F. WEBB. Method of and apparatus for extracting 
precious metals from their ores. The inventor claims, in means for extracting pre- 
cious metals from their ores, the combination of an outer vessel resting in suit- 
able trunnions for containing the reagent or chemical solution, and having inlet 
and outlet pipes communicating, respectively, with the top and bottom thereof 
through said trunnions, a perforated vessel in said outer chamber, and adapted to 
receive the crushed ore, and provided with a manhole opening extending to the \> 
outside of the latter, and means for reciprocating the inner vessel and for rotating / 
the outer vessel on its trunnions, whereby the contents of the inner vessel may be tf 
discharged. Also, the method of separating precious metals from their ores, con- | 
sisting in placing the disintegrated or crushed ore in a closed perforated vessel I 
and causing the latter to reciprocate in the reagent or chemical solution, whereby ' 
the latter is enabled to more effectually act upon the ore. 

497856 May 23, 1983. C. G. BROWN. Ore-tank. In a tank for leaching or 
saturating ore, the combination with a false bottom and a piece of textile material 
laid upon the upper side of said false bottom; of a series of vertically disposed ^ 
perforated tubes designed and adapted to hold the pieces of ore apart and pro- 
mote the circulation of the leaching or saturating solution. 

525970 September 11, 189 4. J. STOKER and B. T. LACY. Method of and appa- 
ratus for dissolving, leaching, and filtering. The inventor claims the improved 
method of dissolving, leaching, and filtering, consisting, essentially, in connecting 
a plurality of closed tanks in series, then introducing an expansible medium upon 
a body of non-compressible fluid contained in a terminal tank to force the said 
fluid under pressure into the successive tanks and through the material under 
treatment until it reaches the final tank, then connecting this last-named tank 
with the initial tank, and finally introducing pressure in the said final tank to v 
force the fluid therefrom so that it may be returned to said initial tank. And in an 2 
apparatus for dissolving, leaching, and filtering, the combination of the tank 
adapted to contain the material to be treated, a tank adapted to contain a non- 
compressible fluid and connected with a source of steam, gas, or vapor supply, a 
valve-controlled pipe from said fluid tank to said material-containing tank, a final 
tank beyond the material-containing tank, a valve-controlled pipe connecting said 
material -containing tank with said final tank, whereby the fluid is forced into said 
final tank, a valve-controlled pipe connecting said final tank with the initial fluid 
tank, and means for admitting an expansive medium into said final tank to force 
the fluid therefrom back into the initial tank. 

530397 December 4, 1894. N. H. CONE. Filter-barrel. In an apparatus 
of the class described, the combination with a revolvable cylinder having a hollow 
trunnion, and a head provided with radiating channels having independent valves 
of a filter arranged in said cylinder and valves for opening or closing said channels 
independently of each other. 


536981 April 2, 1895. T. L. WISWALL and J. B. FRANK. Receptacle for 
recovering precious metals from solutions. This invention relates to apparatus 
wherein the recovery of the precious metals from cyanide and other solutions is 
effected by passing thq solutions through a filtering material, by which the precious 
metals are precipitated. And the inventor claims, in apparatus for the extrac- 
tion of precious metals from solutions, the precipitating box, having an undulating, 
sinuous passage from end to end, comprising a series of alternate angular depres- 
sions and elevations, provided with a series of retaining pins, attached to the interior 
of said precipitating -box, and extending into the precipitating, filtering material 
within said passage. 

549177 November 5, 1895. T. L. WISWALL and J. B. FRANK. Apparatus 
for recovery of precious metals from tJieir solutions. The inventors claim in appa- 
ratus for the recovery of precious metals from their solutions a precipitating box 
adapted to contain a finely subdivided, metallic, precipitating reagent, divided 
into a series of compartments by removable perforated partitions, said partitions 
being provided with adjustable gates, controlling the flow of said solution through 
the perforations in said partitions for the purposes indicated. 

549622 November 12, 1895. P. ARGALL. Apparatus for extraction of precious 
metals. The specifications set forth that in the treatment of ores by the cyanide 
process to extract their gold and silver contents, it is the usual practice to place 
the ores in open leaching-tanks and allow the cyanide solution to percolate through 
the mass and so dissolve and remove the precious metals in solution. This method 
is on the whole fairly efficient, but it occupies considerable time (forty to eighty 
hours) and causes a large consumption of cyanide through decomposition, owing 
to its long contact with the ore and atmosphere. With many classes of ore, how- 
ever, it is found that agitation of the ore and solution is necessary in order to obtain 
the best results or largest extraction of precious metals. Particularly is this the 
case with silver-bearing ores or ores parrying considerable value in silver. 

The agitators heretofore in use shorten the time necessary to dissolve the precious 
metals; but they invariably cause a large consumption of cyanide, due chiefly 
to the continuous agitation of the solution in open tanks or in partly filled barrels 
in the presence of an excess of air, while the ore when discharged from the agita- 
tors is in such a condition that very often it cannot be leached, or at best but 
part of the cyanide solution containing the dissolved gold can be separated from 
the ores. Then again, the agitators now in use are of such small capacity as to 
add largely to the cost of treating the ores. 

This invention relates to a new machine for treating ores by continuous agita- 
tion and continuous percolation under pressure or by means of vacuum and either 
with or without external or additional heat. And the inventor claims a perco- 
lator for treating ores by the cyanide process comprising an outer shell capable 
of being closed, air-tight, hollow trunnions upon which said vessel rotates, con- 
centric tubes extending axially through the vessel, the outer tube being covered 
by a filtering medium, a passage connecting the annular space between the tubes 
with one of the hollow trunnions, and a pipe communicating with the chamber 
surrounding the outer tube. The invention includes other features of a minor 
or subsidiary character. 

552807 January 7, 1896. H. G. WILLIAMS. Method of and apparatus for 
extracting metals from their ores. In an apparatus for the extraction of precious 
metals from their ores by the wet process, the combination of one or 
more castings, with screw conveyers and mixers, means for feeding the solid 
and liquid matters thereto, and a dam placed at the discharge end of the 
casing for each conveyer, having its surface inclined upon the side next to 
the conveyer flights or blades, for the purpose of maintaining the admixture 
of the liquids and solids by preventing the liquid from traveling faster than the 
solid and still giving passage by reason of its incline to the travel of the solids over 
the same; and, in the extraction of precious metals from their ores by the wet 
process, the method of continuously and uninterruptedly precipitating and sepa- 
rating the metals, which consists in simultaneously introducing the precipitating 
agent. and an independent agitating blast of steam into the solution of metal in 


direction as described to secure admixture and agitation by a whirling motion 
and the agglomeration of the precipitated particles of metal, and continuously 
separating the precipitate by settlement and filtration. 

567144 September 8, 1896. S. B. LADD. Apparatus far leaching ores. The 
object of the present invention is to provide an economical and practical apparatus 
for the lixiviation of ores, and particularly applicable to cases where a large mass 
of material has to undergo treatment as, for example, in the lixiviation of low- 
grade gold ores by the cyanide process and where the expense of handling mate- 
rial becomes an important factor with respect to the commercial working of the 
process. The invention applies, genetically, to the lixiviation of comminuted 
or pulverized material of any character, but it is especially designed for the lix- 
iviation of ores by the cyanide process, for in the treatment of ore pulp or slimes 
by the cyanide and other like processes a large amount of material, often of a low 
grade, has to be subjected to the action of an aqueous solution of a cyanide or 
other solvent, or to the successive action of a series of solutions. The common 
course of procedure in working the cyanide process on a large scale is to run the 
ore pulp into large vats and then to cause the proper solutions for leaching out 
the precious metals to percolate therethrough, for example, first an alkaline solu- 
tion, when the ore is acid, then a strong solution, then a weaker solution, and finally 
water to wash the pulp. The vat is then emptied and refilled with fresh ore pulp; 
also, the solvent process is sometimes worked by agitating the pulp and leaching 
solution in pans or vessels. Both systems require considerable labor and are 

Another object of the present invention is to provide means to make the extrac- 
tion process continuous, so that the ore pulp shall progressively and continuously 
be associated with the solutions or the washings which may be necessary for thor- 
oughly exhausting the values from the ore. This is accomplished by construct- 
ing a leaching-tank, in the form of a long trough, which may be divided by one 
or more fixed or removable bridges into so many trough sections as are required 
for the several solutions or washings when one leaching is not sufficient; or by 
providing a series of tanks or troughs operatively arranged with respect to each 
other, employing in connection therewith a conveyer for the ore pulp adapted 
to continuously feed the pulp with a steady movement through the several solu- 
tions in an uninterrupted flow through the apparatus to the point of discharge 
without any intermediate stoppage or handling of the same whereby the lixivia- 
tion of the ore is effected. 

For the purpose of rendering the operation continuous, provision is made for 
a constant drawing off of the charged solution or solutions from the leaching 
troughs and an inflow of fresh solution thereto. In the case of the first cyanide 
solution the inflow is preferably at the ore-entrance end of the trough or trough 
section and the current is with the ore, thus catching the fine float gold carried 
by the fresh pulp; but in the subsequent troughs or trough sections, and also 
in the first, if preferred, the inflow of the solution, (or washing water) is prefer- 
ably made at the ore-exit end and the outflow of the solution is at the opposite 
end where fresh ore or pulp is entering the trough or trough section. Thus, in 
this latter case, the flow of the solution is opposite to that of the ore. The fresh 
cyanide solution first acts upon pulp which is largely leached out, and as the solu- 
tion becomes more and more charged with the gold or precious metals it meets 
Eulp that is progressively richer in the metals, and the conditions are therefore 
ivorable for effecting a complete extraction of the precious metals by the sol- 
vent. As a preferred form of conveyer, slowly-moving blades transverse to the 
trough or tank are used. These blades extend across the tank with just enough 
room at the sides for clearance, and they reach from above the surface of the solu- 
tion down to and into the ore pulp on the bottom of the tank with openings or 
notches in or along the lower part of the blades for the underflow of the solution. 
These blades divide the trough or tank into a number of communicating divisions 
and form what may be called "traveling partitions," moving slowly through the 
trough from end to end thereof. The lower edges of these blades are preferably 
fashioned with rake teeth, and they open up and rake along the layer of ore pulp 
on the bottom of the tank and effect a slow and progressive movement of the mass 

354 t APPENDIX. 

with a constant plowing therethrough and exposure of fresh portions thereof to 
the action of the solution, while the solution in the tank as the series of blades 
move forward has to flow back through the notches or openings in the bottom 
of the traveling blades from each of these divisions formed by the blades, re- 
spectively, into the adjacent rear division, and thus there is secured a constant 
and steady underflow of the solution in close proximity to the agitated pulp. This 
flow of the solution is in addition to and distinct from the flow due to the con- 
stant addition of fresh solvent at one end of the trough and the drawing off of 
the charged solution at the other end thereof; but it will be seen that the under- 
flow thus effected prevents a mere surface flow of the solution from one end of the 
trough to the other. On the contrary, as the flow from the respective divisions 
of the trough is from the bottom and under each traveling partition or blade, the 
overflow or discharge from the trough at the end is necessarily of the charged 
portion of the solution. It will be seen that this method of leaching ores places 
the ore and the solvent under perfect control, which is a very great advantage 
with respect to the economical leaching of ores. There is an agitation and con- 
stant shifting of the pulp in the solution, which very much accelerates the action 
of the solvent and shortens the time required therefor, and the speed of the con- 
veyer can be regulated so that the pulp will not remain in the tank or tanks any 
longer than is necessary, and -yet long enough for the extraction of all value there- 
from. On the other hand, the flow of the solvent through a tank can be gauged 
so that it will issue from the tank fully charged or charged to the degree most 
profitable under all the conditions of the case. 

576118 February 2, 1897. W. F. HEATHMAN. Means for extracting gold and 
silver from sea-water. In order to extract said metals, the sea-water or salt lake- 
water is passed through a filter made of carbon, and the gold and sliver held in 
solution in the sea-water or salt lake-water are freed from the chemical combina- 
tions in which they occur in the water. The chlorides and bromides of gold and 
silver in solution when passing through the carbon filter are decomposed by the 
reducing power of the carbon, the liberation of chlorine, and the destruction of 
the bromine combination, with the result that metallic gold and silver are pre- 
cipitated in the carbon filter and deposited in the pores and upon the surface of 
the carbon. And the inventor claims a tank mounted on suitable supports and 
provided in its side with an inwardly opening valve or gate, said tank having a 
perforated bottom, and a filtering medium arranged on the bottom and comprising 
alternating layers of coarse and fine carbon, a layer of wire-cloth, and a perforated 
top covering. 

584627 June 15, 1897. J. J. DEEBLE. Apparatus for extracting gold from 
auriferous material. This invention has been devised in order to provide a machine 
for use in the extraction of gold from auriferous material by the aid of chemical 
solvents, in order to insure the particles of auriferous material being brought into 
intimate contact with the cyanide or other solvent solution. It includes a vat 
or pan to receive the auriferous material to be treated, having at or about its cen- 
ter a vertical shaft or spindle with one or more agitators or stirrers attached to 
its lower end. Motion is imparted to this shaft or spindle by bevel gearing or 
other convenient mechanical contrivances, and means are* provided for reversing 
the rotation and controlling the speed of the agitators, as well as for raising or 
lowering the agitator shaft or spindle. These means may consist of a screw- 
threaded lifting rod with correspondingly threaded bevel wheel in gear with a 
bevel pinion fitted with a crank-handle, whereby it may be rotated in the required 
direction; or, if preferred, a rack and pinion may be used for the purpose. The 
inner side of the wall of this vat or pan is provided with a series of projections 
which produce eddies or swirls in the material under treatment as it is carried 
round the vat or pan. In order to drain or draw oft 7 the gold-bearing solvent from 
said vat, it is provided with a vertically sliding valve A waste discharge valve 
may also be provided in the lower part of the vat or pan for the purpose of enabling 
the waste material to be sluiced therefrom after the gold has been dissolved and 
the gold-bearing solution has been drawn off through the valve above referred to. 

587408 August 8, 1897. H. L. SULMAN. Method of recovering precious metals 
from their solutions. This invention has for its object the recovery of precious 


metals from solutions of the same by means of a new and improved apparatus, 
the apparatus being constructed to effect the deposition or " precipitation " of 
the precious metal or metals in solution upon a " precipitating " substance or 
" precipitant " which is in a solid but more or less finely divided state. 

The apparatus is designed to recover these metals from solutions of their haloids 
by means of the employment therein of dense but more or less finely divided car- 
bon, subsulphide of copper, or other suitable precipitant; again, also, for the 
recovery of the same metals from their cyanide solutions by means of the finely 
divided zinc product commercially known as " zinc fume," and generally for analo- 
gous requirements. 

It is necessary that whatever the nature of the precipitant used and the degree 
of fineness to which it is found desirable to reduce it primarily, it shall be of greater 
specific gravity than the liquid or solution desired to be precipitated by it, so that 
the precipitant shall tend to settle from the liquor by gravitation. Further, it is 
necessary to this invention that the solution or liquor to be precipitated shall per- 
colate upward through the mass of solid finely divided precipitant. 

In an apparatus with parallel vertical sides the upward flow of liquor would 
tend to carry off finely divided particles of precipitant unless special means were 
taken to prevent this. Filters tend to become clogged and are generally useless 
for this purpose, so that the inventor retains the particles of the solid precipitant, 
upon whose surfaces the precious metals are in course of deposition, within the 
apparatus by inducing the subsidence of them. This is effected by continually 
reducing the upward rate of liquor flow, which is secured by constantly increasing 
the area of the liquor column as it rises higher in the apparatus. 

The apparatus takes the form of a funnel. The liquor enters (under a suffi- 
cient pressure or "head") through the bottom orifice. It then meets with and 
thoroughly mixes with the mass of finely divided precipitant in a condition of 
suspension in the liquor. The solid, finely divided particles do not sink against 
the comparatively rapid inflow, or are prevented from doing so to any extent, 
by means of an automatic valve of ordinary type. By this intimate admixture 
of liquor with precipitant the deposition of the precious metals in solution in the 
former is effected upon the minute surfaces of the latter. It now only remains 
to remove the depleted liquor from the particles of the solid precipitant containing 
the gold, silver, etc. As the liquor continues its upward flow by virtue of the 
continually diverging sides of the apparatus the area of the liquor column becomes 
greater and greater. The rate of the vertical upflow is thereby correspondingly 
reduced. This continues until a point is reached at which the upflow is vertically 
so slow that the finest particles are able to settle or subside against it. At any 
point, therefore, above this limit or "zone," the absolutely clear liquid may be 
drawn o^ from the apparatus free from suspended particles and depleted of its 
precious-metal contents. 

If the precipitation of the precious metals be deemed to be incomplete in one 
apparatus, owing to the richness of the original liquor or to other causes, the outflow 
may be caused to pass into a second similarly arranged apparatus or through two 
or more such apparatus placed in series; but in general one apparatus can be made 
to secure practically perfect removal of the precious metals dissolved in a given 
liquor by the use of a suitable precipitant. If a series of two or more of such appa- 
ratus be employed, the first of the series may be used to enrich quantities of pre- 
cipitant which have only been partially used up to their fullest capacity of pre- 
cipitating the precious metals, while the succeeding members of the series are 
supplied with the necessary amounts of less rich or quite fresh precipitant in order 
to remove any remaining traces of gold, silver, etc., which may escape unpre- 
cipitated in the outflow from the first apparatus. The poorer precipitates in these 
last apparatus are in course of time removed through the bottom of the apparatus 
and transferred to the first one of the series, there to be enriched to their full 
capacity, while their place is taken by fresh quantities of poorer or quite unused 
precipitating agent, and so on. 

When the precipitate is deemed to be sufficiently rich, it is removed from the 
apparatus by a " three-way cock" at the bottom thereof, or by other suitable* 


arrangement, and the precious metal it contains finally recovered by any suitable 
method, such as in the case of the employment of a carbon precipitant by burning, 
or in the case of the use of a zinc precipitant by smelting. 

The apparatus is also supplied with a small central funnel for the introduction 
of fresh quantities of precipitant from time to time to the point of maximum pre- 
cipitating action in the apparatus, i.e., near the inflow. By providing this funnel 
with a bell-shaped or inverted funnel termination a sort of "chamber" is produced 
in the lower part of the apparatus having an annular space for the passage of liquors 
between the rim of the smaller funnel and the sides of the large one. This chamber 
is of considerable aid in promoting the action of the precipitant by keeping the 
bulk of it constantly near the liquor inflow and securing perfect admixture by 
means of the vortex currents, etc., it induces. It is further desirable to break 
up the rapid rush of inflowing liquors at their point of entry into the apparatus 
and to secure their subdivision and intimate admixture with the precipitant as 
early as possible. This is effected by capping the end of the inlet pipe with a 
small perforated cone or "distributer." The perforations may be from one-fourth 
to one- tenth the diameter of the inlet pipe, but their total area must be larger than 
that of the sectional area of the pipe. The holes may be bored in a direction 
perpendicular to the cap cone or they may be made "tangential," i.e., bored at 
a tangent to the internal circumference of the cone, thus securing a rotary initial 
flow of the inflowing liquors instead of a series of straight streams. In the major- 
ity of cases, however, perpendicular bore holes answer equally well. 

The clear precipitated liquor may be drawn off at any point above the limit 
of subsidence either, by a pipe, or, preferably, by allowing it to flow equally over 
the rim circumference of the apparatus. The latter method secures the quieter 
and more uniform outflow and does not disturb the top layers of liquor under- 
going final subsidence by establishing a quick current in one particular direction. 

If desired, the rim may be encircled with a filter-screen of lawn, calico, or other 
filtering or straining medium, so as to retain within the apparatus any particles 
of precipitant which may be floated or "buoyed up" by bubbles of air or other 

The clear liquors passing over the rim and through the precautionary filter or 
strainer fall into and are collected by a circular trough or "launder," attached 
to the apparatus below the rim, whence they are conveyed away by a pipe. As 
before stated, this may lead into a storage-vat or into another similar apparatus, 
or, if deposition of the floating particles is not absolutely complete, into any suitable 
type of apparatus such, for example, as the slat-partitioned tank used for freeing 
softened water from traces of deposit where subsidence is finally rendered abso- 
lute. In most cases where the traces of precipitant have escaped, I have secured 
perfect final subsidence by allowing the liquors to flow through a shallow tank 
of from four to six times the area of the top of the precipitating apparatus before 
passing them direct to the storage liquor vats. 

Such an apparatus as is described is termed a " precipitating cone." It may 
be constructed of any suitable material, such as wood, stoneware, galvanized 
iron, etc., according to the nature of the liquor or precipitant it is designed to 
treat. Its action, until the charge of precipitant it contains is exhausted and 
requires renewal, is perfectly automatic and continuous. Its capacity, its height, 
the angle of its f'des, the ratio diameter of inflow pipe to top area of cone will 
naturally vary with the volume of liquor to be dealt with, the rate and head of 
liquor inflow, the relation of the specific gravity of the liquor to that of the finely 
divided precipitant, the actual coarseness or fineness of the particles of the latter, 
and so on. These data may be calculated or decided by preliminary experiment 
in any particular case. As an example, however, of the application of this in- 
vention to the recovery of gold bullion from cyanide solutions, the following dimen- 
sions of the apparatus are cited: For a flow of from 600 to 800 gallons per hour 
B depth of 5 feet, with a top diameter of 5 feet, is amply sufficient. The diameter 
of the inlet pipe is from 1-J to If inches, according to the head of the inlet liquor, 
Awhile the perforations of the cap cone or distributer are three-sixteenths of 1 inch 


in diameter. The charge of zinc fume in such an apparatus varies from 5 to 30 
pounds, according to requirements. 

587874 August 10, 1897. E. D. SLOAN. Barrel-filter. The object of this 
improvement is to provide a suitable filter-barrel, with a durable and highly 
effective filter, at comparatively low cost. With a view to securing the 
desired ends the usual trunnioned iron barrel is lined with lead. The framing 
of the filter-bed is composed wholly of suitable wood capable of fairly resist- 
ing the action of chlorine and acids, and which may be filled with suitable 
matter to enable it to better resist the destructive action of the corrosive solutions. 
The filtering medium is composed of material which resists the solutions, is well 
protected against undue abrasion due to the action of the solid matter during 
the rotation of the barrel, and it has its filtering area supported to enable it to 
safely bear the overlying contents of the barrel by an underlying floor of such 
metal as will practically resist the action of chlorine and sulphuric acid as, for 
instance, a lead floor and the latter is freely perforated to admit of the prompt 
discharge of the filtered liquid. The filtering surfaces are flat, and hence the body 
of any woven filtering medium is maintained in a condition more favorable to the 
passage of the liquid than would be the case if it occupied a curved line and said 
surfaces were concave in conformity with the interior contour of the barrel. The 
framing of the filter-bed involves inexpensive straight work, as distinguished from 
the curved or segmental work in framing, which is made to conform to the interior 
of the barrel as heretofore, and the filter-framing is constructed in parts which 
are so interlocked as to secure rigidity, but which may be readily applied to or 
removed from the barrel by way of the usual manhole and without deranging 
the lead lining or the means by which the lining is clamped to the barrel. 

597372 January 11, 1898. P. J. DONOHUE and J. F. CORKER. Precipitating 
safe. The combination with a closed vessel or standpipe provided with a normally 
closed outlet at its bottom for the precipitate and having a body or column of 
zinc filings or like material in its upper part, adapted as corroded to fall into the 
lower part, of means for supplying, under pressure, the solution containing the 
precious metal to the lower end of said body or column of filings or like material, 
to cause the corrosion or oxidation thereof, whereby such corroded or oxidized 
portions will gradually precipitate to the bottom of the vessel or standpipe and 
the fresher portions of the filings or like materials be exposed to the ascending 

606810 July 5, 1898. J. W. PACK. Recovery of gold from waste solutions of 
chlorinaiion works. A means for recovering gold from waste solutions of chlorina- 
tion works, consisting of a tank having an inlet passage at the lower portion and 
an outlet passage at the upper portion and having metallic aluminum contained 
therein, and intermediate between the inlet and outlet passages of the tank, and a 
filter fixed within the tank between the metal and the outlet passage and having 
its lower side coated with a substance which will arrest the fine precipitated gold 
and prevent it from passing off with the liquid. 

608554 August 2, 1898. R. MOODIE. Washing or leaching apparatus. In 
an apparatus for washing or leaching, a series of cells, one of which is a dry 
cell and the others of which contain washing or leaching liquid, means for intro- 
ducing the material to be washed into the dry cell, an oscillating shaft extended 
longitudinally of the series of cells, means operated by said shaft to transfer the 
material from the dry cell to the washing cell next in series, arms attached to the 
oscillating shaft and extending one into each washing cell, and scoops on said arms. 

608945 August 9, 1898. H. B. WILLIAMS. Lixiviation apparatus In a 
lixiviation apparatus, the combination of a vertical series of annular tanks 
arranged one above another and each provided with an exit through which ore 
or other substances may be discharged into the tank beneath, each tank bottom 
being provided with an ascending incline leading to one side of the tank exit and 
having a descending incline on the other side, means for feeding ore into the top- 
most tanks, pipes for conveying leaching solution into the several tanks separately, 
the feed of the ore to be continuous and the feed of the solution to be continuous 
or intermittent, filters located in the several annular tanks, and automatic scraping 


and stirring mechanism to cause the ore and solution to be moved around each 
annular tank and over the filter therein. 

610596 September 13, 1898. R. AYMER and D. J. NEVILL. Filter-frame. 
In a filter-barrel, the combination of a rubber grating having a corrugated 
surface in contact with the curved inner lining and periphery of said filter-barrel 
adapted to allow the filtering solutions to run along and down the lining of said 
barrel, a perforated bedplate of glass or porcelain curved concentric with the inner 
periphery of said barrel and resting on said rubber grating, a filtering medium 
on said glass bedplate, a curved glass grating resting on said filtering medium, 
two oppositely disposed cleats secured lengthwise of said barrel to its inner periphery 
adjacent to the ends of said curved glass bedplate and grating, and wedge keys 
between said ends and said cleats adapted to key said members against the barrel. 

611515 September 27, 1898. J. P. SCHUCH, Jr. Means for extracting precious 
metals. In a metallurgical apparatus for treating ore by a cyanide solution, a tilt- 
able tank comprising a suitable support, a tank body having a discharge gate at its 
rear end and pivoted to a support at a point between its centre and the front end, 
a drain device in the bottom of the tank for drawing off the cyanide solution, 
holding springs mounted on the support and engaging with the tank body at points 
between its discharge end and the pivotal connection thereof with the support, 
and means for retracting the holding springs from engagement with the tank body. 

611935 October 4, 1898. J. POOLE. Process of and apparatus for treating ore 
tailings. For the continuous treatment of pulps, slimes, tailings, and the like with 
cyanide and similar solvent solutions and in combination, a series of shallow tray- 
like baths, a rake in each bath of the series for reciprocating the rakes, an overflow 
chute at the end of the series, settling-tanks to receive the overflow from the chutes, 
means for separately discharging the solid and liquid contents of the tanks, con- 
veyers adapted to raise the solid contents from one tank after discharge, a launder 
in which such contents are received and in which they may be further treated 
with a solvent solution or wash, and a further settling-tank for receiving the dis- 
charge from the launder. 

615968 December 13, 1898. T. CRANEY. Apparatus for treating ores, etc. 
In an apparatus for treating ores, the combination of a tank adapted to contain 
a body of the ore to be treated, devices for feeding ore into the top of said tank 
and discharging it from the bottom thereof at a point above the tank in a con- 
tinuous manner, a solvent supply reservoir, a receiver connections between the 
tank and said supply reservoir, and receiver for producing a continuous flow of the 
solvent through the tank in a direction opposite to that of the movement of the 
ore, an endless-chain carrier in proximity to the tank and having draining buckets 
adapted to receive the ore discharged from the tank, means for discharging a liquid 
upon the drainage buckets, and means for collecting the drainage from the buckets 
and returning it to the aforesaid supply reservoir. 

617029 January 3, 1899. W. A. K 6 NEMAN and W. H. HARTLEY. Apparatus 
for separating liquids from solids. The method of abstracting liquid from finely pul- 
verized ore, ore slimes, or other solids impervious to percolation with which the 
liquid is mixed, which consists in subjecting the mixture to gaseous pressure ap- 
plied above the same, and simultaneously to the action of a partial vacuum ap- 
plied below the same, removing a portion of the liquid by filtration below the body 
during compaction of the solids, and collecting and abstracting by pressure the 
remaining liquid above the compacted solids. 

617497 January 10, 1899. P. ARGALL. Cyanide -filter-tank. In a cyanide 
filter-tank, a vertical metallic side or wall, a horizontal bottom secured thereto, 
having a central opening, a packing ring secured to the inside of said wall, near 
the bottom, with a spacing, a system of level joists converging from the perimeter 
toward the center, upon said horizontal bottom, a plastic filling between said 
joists sloping downward from the packing ring regularly toward the central open- 
ing, a level floor with interstices laid upon said joists, permeable filtering material 
upon said floor, and a covering of textile fabric, the outer margin of which is packed 
into the crevice between the packing ring and the vertical wall. 

618622 January 31, 1899. P. SOMERVILLE. Apparatus for extracting metals. 
An apparatus for extracting metals, consisting of parallel barrels having annular 


disks closing one end with central inlet openings for the material, a framework 
and roller support for said barrels, means whereby the barrels are rotated in oppo- 
site directions, spiral flanges fixed to the interior of the barrels for advancing the 
material therethrough, devices for feeding material and fluid matter to the upper- 
most barrel, means for separating the coarse from the fine material and delivering 
them separately, and means for transferring material from the discharge end of 
one barrel into the inlet end of the barrel below. 

619211 February 7, 1899. A. M. NICHOLAS. Filtering apparatus for separating 
gold- and silver-bearing solutions. This invention has been devised for the pur- 
pose of providing means whereby solids or insoluble material may be separated 
from liquids carrying same in suspension, but more particularly for the purpose 
of providing means whereby the separation of gold and silver-bearing solutions 
from tailings, slimes, pug, or pulverized ore may be carried on continuously and 
in such a way that a clean or partially clean filter-cloth will be continuously brought 
into operation without necessitating stoppages for recharging, as required with 
the appliances at present in use. 

The essential feature of the invention consists in the use of a rotating-wheel, 
disk, or table formed with a series of air-tight compartments covered with cloth 
or other filtering material supported upon a metal sqreen or perforated plate and 
adapted to be automatically placed in communication with a vacuum pump in 
turn for a sufficient time to enable the liquid to be drawn through the filtering 
material, leaving the solid constituents upon the filtering surface, whence they 
can subsequently be removed by brushes, jets of water, scrapers, or similar con- 
trivances, provision being made for automatically allowing air to enter into the 
various compartments at the desired period of the operation to facilitate the removal 
of the solids from the outer surface of the filtering material. 

620660 March 7, 1899. J. LUCE. Apparatus for treating ores by lixivia- 
tion. In a tank for the treatment of ores, a lining composed of asbestos applied 
to the inner side of the tank, the notched or recessed boards applied inside of the 
asbestos, and the steam pipes placed in the notches in the boards, combined with 
two thicknesses of grooved perforated boards, and the layers of cloth between 
the boards. 

623465 April 18, 1899. G. S. DUNCAN. Apparatus for separating gold- and 
silver-bearing solutions from ores or slimes. Hitherto upward percolation has been 
used for the displacement of the various gold- and silver-bearing solutions in the 
treatment under the cyanide or other similar processes of tailings or free leaching 
ores which are not in the form of slimes. With this upward percolation false bot- 
toms for the vats with webbing upon them have been used and the solutions have 
been introduced underneath these false bottoms, which have acted as distributors 
therefor and allowed them to pass evenly up through the free leaching ore, dis- 
placing the gold- and silver-bearing solution contained therein. This false bot- 
tom and webbing are adapted for use with free leaching ores only and cannot be 
employed for displacing solutions used in treating very finely crushed ores or limes 
which do not leach freely. /\ * 

The present invention has been devised in order that the various solutions 
may be displaced, as above described, from finely crushed ore or slimes, without 
the aid of any false bottom and filtering webbing. And the inventor claims, in 
an apparatus for separating solutions of the precious metals from residual ores 
and slimes, the combination with a leaching- and displacement-tank or vat and 
with a vat to hold said solutions, the latter being placed at a higher level than 
the former, of a series of pipes to convey said solutions from the higher vat, the 
discharge ends of said pipes entering the leaching-vat, a series of hoods having 
slightly arched portions which overlie the said discharge ends, and stirring arms 
radiating from a central shaft in said vat, the arched portions of the hoods being 
arranged in radial lines, or at right angles to the movement of currents set up by 
the stirring arms. 

623772 April 25, 1899. A. F. DUEY. Apparatus for leaching ores. A device 
for treating pulverized ores, comprising a leaching-tank, an air-compressor, a 
tank for storing the leaching liquid, a perforated pipe in the bottom of the leach- 


ing-tank, connections from the air-compressor and liquid-storing tank to the per- 
forated pipe, a perforated drainage pipe in the bottom of the tank, and a layer 
of filtering material about said pipe. 

? May 9] 1899. C. H. PEAD. Slime filter. The apparatus consists 
of a tank fitted with a hood of conical or any other convenient form. The sides 
of the tank project above the point of attachment of the hood, so as to form an 
annular space to act as a receptacle forming a launder for discharge of the clear 
liquid. In the center of the hood is an opening, around which is riveted or bolted 
a frame or seating arranged to carry a niter composed of one or more layers of 
niter-cloth or any other well-known filtering medium. The filter is kept in place 
by means of a protective gird of clamp of suitable form and strength to resist the 
effective pressure from the interior of the tank. A number of small distribution 
pipes set at such an angle as to cause the slimes to impinge on the under surface 
of the filter are connected to the seating of the latter, through which they pass. 
They are connected to a main distributer, which in turn is connected with the 
delivery-pipe or column of the slime-pump. One or more taper-shaped plugs 
or cores constructed of light steel tubes, their number varying according to the 
.size of the tank, pass through the hood and extend to the bottom of the tank. 
They taper from about 18 inches at the top to 15 inches at the bottom. They 
are fitted at their upper ends with a flange, to which is attached a shackle. Their 
lower ends are closed by means of a dished bottom riveted in place and having 
a strong bolt or stud fitted to its center. Each plug or core rests on a seating 
fitted to the outside of the hood and through which the plug or core posses. The 
seating is attached thereto by means of its flange. 

In the bottom of the tank and directly under the aperture in the hood through 
whi2h the plug or core passes is a discharge door of the ordinary manhole or other 
convenient type. The end of each plug or core passes easily into the discharge 
opanin^, and the discharge door is drawn up onto its seating or joint by means 
of the bolt or stud on bottom of the plug or core and by its nut. The plugs or 
cores when in place and holding up the manhole doors' afford an effectual means 
of resistance against internal pressure. 

A special pipe is arranged and fitted to the upper portion of the tank to drain 
the space forming a launder between the top of the tank and the upper surface 
of the hood and to conduct the liquid portion which has passed through the filter 
to the precipitation boxes or to waste. 

? May 9, 1899. F. A. EDWARDES. Apparatus for use in treating metallic 
ores. In apparatus for use in the treatment of metallic ores, the combination 
with an annular vat having a stirrer moving therein and skimmers attached to 
and moving with the said stirrer, of means for tipping the said vat for discharging 
the contents. 

624957 May 16, 1899. L. H. MITCHELL. Tank-bottom discharge door. A 
discharge apparatus for tanks provided with a hollow upper portion, a base having 
integral-bearing zones connected thereto at one end thereof, a casting having an 
upper annular supporting rim and adapted to receive said bearing zones, a ring 
surrounding said casting, devices connecting said rim and ring to secure the casting 
in position, and means supported by said casting to unseat said base. 

624.958 May 16, 1899. L. H. MITCHELL. Tank-bottom discharge door. A 
discharge apparatus for tanks consisting of a casting secured in the bottom of 
the tank, a ring below the tank around the casting, and means for securing the 
rim and ring in position, a funnel above the casting, a base connected with the 
lower end of the funnel and provided with an annular offset or shoulder, a pack- 
ing-ring within the offset, and adapted to rest upon the rim of the casting, a plate 
or bar bearing against the rim of the casting, a nut-carrying screw in the plate 
or bar adapted to engage the base and draw the same within the casting, a brace 
or clamp connected to the plate or bar above the nut on the screw, and means 
for rotating the screw. 

639540 December 19, 1899. W. DUNCAN. Means for mixing and aerating 
sands or tailings while under treatment by solvents. Numerous attempts have from 
time to time been made to secure the thorough mixing of sands and tailings, includ- 


ing slimes, with- the solvent while under treatment and also to prevent that close 
packing which prevents the percolation of the solvent and wash liquors. For 
this purpose vertical vessels with vertical agitators, revolving barrels, and air, 
steam, and water jets have been used, but these means have not been as efficient 
as they might be. 

This invention relates to improved mechanical means for mixing and aerating 
"sands" or "tailings," by which terms are included slimes, sludges, and con- 
centrates, while under the action of solvents, whereby time is saved and a better 
extraction is obtained; and it consists of a semicircular vat provided with a re voluble 
agitator composed of arms arranged helically on a shaft running the length of 
the vat. At one end of the vat is placed the fast and loose pulleys and gear 
for slowing and rotating the agitator, while at the opposite end a series of taps 
are provided connected to the vat at various heights and to pipes, so that the 
liquor can be drawn off at any desired point and either run direct to the sump or 
through a filter to the sump. 

641419 January 16, 1900, H. C. WHEELER. Agitator. In an agitator, the' 
combination of the vat, the track provided with the cog-rack, the carrier pro- 
vided with the pinion meshing with the cog-rack, the first driving-shaft provided 
with the driving-pinion, the driven cog-wheel meshing with the driving-pinion, 
the gear-wheels connecting the driven cog-wheel with the pinion meshing with 
the cog-rack, the agitator-frame journaled or pivoted to the carrier-frame, the 
second driving-shaft journaled in the agitator-frame, the agitators journaled in 
the agitator-frame and adapted to be operated by the second driving-shaft, inter- 
mediate gearing connecting the second driving-shaft with the driven cog-wheel, 
one of such gears being journaled with its axis in line with the axis of the pivotal 
support of the agitator-frame, and means for rotating the first driving-shaft. 

647358 April 10, 1900. D. W. BALCH. LeacMng-tank. A tank having a 
bottom, a leaching false bottom above the same, and vertical filtering partitions \^> 
arranged in pairs within the tank, whereby spaces are left between pairs of par- 
titions, and other spaces are left between members of such pairs, said spaces last 
named all communicating with the chamber between the bottom and false bottom. 
647678 April 17, 1900. C. W. MERRILL. Means for charging leaching-vcts. 
This invention relates to a method of charging ore or tailings to a leaching-vat, 1 
which process is a step in the treatment of said ore or tailings preliminary to the 
application of the solvent solution in cyanide, hyposulphite, or other hydrometal- 
lurgical processes. 

It consists essentially in conveying the tailings or ore by any well-known 
adaptable mechanical means to a point above the center of the vat to be charged 
arid delivering the material there to a hopper, which feeds a revolving chute inclined 
at an angle greater than the natural slope of the material to be handled, and with 
openings adjustable both as to size and position, through which the material to/o 
be treated falls gently into the vat and distributes evenly, thus giving a charge'"' 
of minimum density and maximum homogeneity, the conditions most favorable 
to successful leaching and dissolution of the precious metals. 

The ordinary method of charging leaching-vats is from cars running on a super- 
imposed track. By this means the momentum of the carload of tailings or ore 
dropping through five or more feet to the bottom of the vat is such as to produce 
considerable, packing and, moreover, an uneven packing or density. For instance, 
in dumping from an end discharge car the resultant mass of ore or tailings will 
take the form of a cone in the vat and the maximum density will be in the center 
of the approximate circle forming the base of the cone and will decrease along" 
the radii toward the circumference of this circle. Furthermore, the variation 
in fineness of the different carloads is not equalized, and a vat charge of ore or tail- 
ings results, which is heterogeneous, both as regards density and as regards fine 
and coarse material. Now, first, the charge of ore or tailings in a vat should be 
of the least density possible to obtain, because experience has demonstrated that 
the greater the permeability, and consequently the greater the amount of lixiviant 
possible to percolate through the charge, the greater the extraction of the precious 
metals in a given time, or, from another standpoint, the greater the permeability 
the less the economic period for leaching, and hence the less the cost for plant 


and subsequent operation; second, the charge should be as nearly homogeneous 
as possible as regards both density and size of material, because in leaching ores 
it is necessary to follow solution with wash-water to replace and prevent the loss 
of the former or to follow one lixiviant with another of different strength or con- 
taining a different solvent, and in doing this to maintain the surface of demarca- 
tion between the one and the other as nearly a horizontal plane as possible in order 
to minimize the mixing of effluent solutions. The above conditions of minimum 
density and maximum homogeneity are produced by means of a revolving inclined 
wide chute with small openings in the bottom, adjustable as to size and position 
transverse to the direction of the stream of ore or tailings. By means of this 
method a number of very small streams of ore or tailings fall gently into the vat 
as the chute revolves, and by increasing the speed of revolution a carload of fine 
or coarse material can be spread over the whole area of the vat, thus giving the 
smallest possible dimension parallel with the course of the lixiviant. 

653631 July 18, 1900, J. C. WALLACE. Filter barrel or tank. In a filter barrel 
or tank, a filtering device consisting of a series of curved metal plates, perforated, 
fastened to the inside wall or walls of said barrel or tank; a filter-cloth upon the 
upper surface of said plates, secured thereon by a series of imposed metal bars 
and filling strips secured in position by bolts or other fastening devices to the wall 
or walls of said barrel or tank. 

653684 July 17, 1900. F. H. LONG! Metallurgical filter. The combination 
with a closed vessel having a filter septum and a regulated outlet port for the fil- 
trate beyond such septum, of the wash-water pipe connected in hydrostatic column 
with said vessel and the external centrifugal pump joined at its separate sides in 
closed union with the opposite ends of the vessel, the journal-box for said pump- 
axle being furnished with a water column pipe to counterbalance the hydrostatic 
pressure at the vessel. 

654315 July 24, 1900. T. E. LEECE. Apparatus for working ores of valuable 
metals This invention relates to an apparatus which is designed for working the 
ores of valuable metals, and is especially useful for separating slimes from solutions 
in which they may occur, and also for separating heavier and lighter parts under 
any condition in which they may be found associated. 

It consists essentially of a tank and an endless traveling belt with directing 
rollers, by which one portion of the belt is caused to travel through the tank in 
close proximity with the bottom and the other part is guided back exterior to 
the tank by similar rollers. It also comprises a means for straining, or separating 
the liquid from the heavier portions. 

660498. October 23, 1900. J. A. FLEMING. Apparatus for leaching ores. 
In an ore-leaching apparatus the combination with the leaching-tank having a 
pulp discharge, of the conical perforated filtering-hopper therein having the dis- 
charge for the pulp, means by which to maintain air pressure below the diaphragm, 
whereby to control the flow of solution through it, means for the introduction and 
withdrawal of chemicals to and from the body of the tank above the filtering dia- 
phragm, and devices for controlling the discharge of the pulp from the tank. 

660499 October 23, 1900. J. A. FLEMING. Apparatus for leaching ores. 
An ore-leaching apparatus, consisting of the leaching-tank, having a filtering- 
hopper a solution discharge below said hopper, and a pulp discharge also below 
said hopper, and independent of the solution discharge, a washing-tank below the 
leaching-tank and in position to receive the pulp from the discharge thereof, and 
means for controlling the passage of the pulp from the leaching- to the washing- 

664059 December 18, 1900. J. P. SCHUCH, Jr. Ore-mixing machine. 
Heretofore, in treating gold-bearing ores by the common cyanide process, the 
ore is first crushed, dried, and rolled to a proper degree of fineness, and that which 
requires roasting is then conveyed to the roasters, while the oxidized ore, which 
does not require roasting, is conveyed to the bin or receptacle therefor. After 
the portions of the ore to be roasted have passed through this step of the process 
the same is conveyed to the cooling-room before being deposited in the bin or 
receptacle referred to which contains the ore requiring no roasting. All of the ore 


is then removed by manual labor into the ordinary stationary cyaniding-tanks, 
and after these tanks are filled with the ore the cyanide solution is introduced 
therein. In this process the filled cyanide-tanks, with the solution and ore therein, 
are permitted to remain filled and unmolested for a sufficient length of time for 
the solution to act on the ore, after which the gold-bearing solution is drawn off 
and allowed to flow to the precipitation-room, while the tailings in the tank are 
then washed with water and shoveled out or sluiced out when this is possible. 
In this process, which is the one usually followed out in extracting gold and silver 
from their ores by the use of cyanogen containing solvents, the percentage ex- 
tracted rarely exceeds 80 per cent, of the ore value, and it is the purpose of the 
present invention to provide means whereby a larger per cent, of the value of the 
ores may be saved. 

To this end the invention contemplates an improved mixing-machine which 
provides for a thorough aeration of the ore and solution, while at the same time 
providing for a mixing of various grades of ore with the cyanide solution, so as 
to make one even grade out of ores of various values. And the inventor claims, 
in an ore-mixing machine, an open tank provided at the bottom with a solution 
drain, a perforated false bottom arranged within the tank above the main bottom 
and supporting filtering material, an ore discharge pipe communicating with the 
interior of the tank immediately above the plane of the false bottom, a revoluble 
agitator depending within the tank into close proximity with reference to the 
false bottom, and a plurality of air jets arranged to communicate with the tank 
in a plane intermediate the said false bottom and the lower end of the agitator 

664196 December 18, 1900. J. C. WALLACE. Filter-bed. In a filter-barrel, 
a filter-bed consisting of a series of metal plates having drain slots or perforations 
therethrough, a series of perforated tiles arranged as a filtering medium upon 
and supported by said metal plates, a series of metal-binding strips imposed upon 
or against said tiles; together with suitable means for fastening or confining the 
same together and to the inner wall of a filter-barrel or tank. 

671028 April 2, 1901. J. R. PHILLIPS. Pulp agitator. This invention con- 
sists of an inclined or funnel-shaped tank or containing vessel into which the pulp 
is placed with water, cyanide solution, or other equivalent liquid, a circulating- or 
suction- and force-pump by which the surface liquid may be drawn from the tank, 
and a pipe extending centrally down to near the bottom of the cone, with a dis- 
charge nozzle through which the liquid is delivered with force, so as to flow upward 
along the sides of the funnel and through the material, whereby the latter is loosened, 
agitated, and prevented from packing. In conjunction with this may be used 
a canvas or equivalent filter lining for the funnel, with means for providing a space 
intermediate between it and the sides of the funnel for the filtering through of 
water, and a means for conducting such filtered water away from the apparatus. 

680154 August 6, 1901, A. D. JANSEN. Discharge door for cyanide-tanks. 
In cyanide treatment the sands are subjected to the action of cyanide solution, 
which solution after the proper length of time has elapsed is drawn off through 
a filter composed of matting or some similar material situated at the bottom of the 
tank. This matting or filtering material does not rest directly on the bottom 
of the tank, but is supported by a grating or perforated false bottom in order to 
allow a free passage for the solution which has filtered through. That portion 
of the tank, therefore, which is situated over the discharge door has no grating 
or filtering material, and consequently a more or less vertical column of sand is 
left in the tank, which still contains cyanide solution with gold in solution, the 
result being that this portion is imperfectly treated. 

The object of this invention is to provide a door so constructed that a piece 
of matting or filtering material may be placed upon it in order that the filtration 
of the solution shall be just as complete over the discharge door as in the rest of 
the tank. 

This invention furthermore relates to an improved construction, whereby the 
door is rendered much more easily closed and also to a system of packing the same 
by which joint between the door and the bottom of the tank is rendered tight. 


683412 September 24, 1901. A. J. PERRY. Ore-separator. The object of this 
invention is to introduce a mixture of steam and air in the pulp, whereby the 
precious metal receives a quick chemical action, with the result that considerable 
time is gained over the method heretofore employed. And the inventor claims, 
in a leaching apparatus, the combination of a receptacle for holding pulverized 
ore, an agitator mounted in said receptacle and having a series of radial horizontal 
pipes each provided with a series of perforations at one side thereof, a series of 
scrapers or blades mounted on said agitator, a pipe adapted to supply to said agitator 
a mixture of steam and air from a proper source, and means adapted to rotate 
said agitator whereby the discharge of steam and air through the perforations 
of said pipes is directed toward the rear while the said scrapers or blades are moving 
in the opposite direction. 

684654 October 15, 1901. C. VOELKER. Ore-filter. The extraction of valuable 
metals from ores through the lixiviation processes, such as the cyanide and others, 
although allowing the advantageous working of low-grade ores, still has one fault, 
that more or less metal remains in the tailings, and thus losses occur caused by 
the slimy particles contained in the pulverized ores generated from clay, talc, 
and other minerals which clog up the meshes of the filtering-cloth, and thus pre- 
vent the solution from going through freely. In such apparatus the ore is intro- 
duced and the solution added, and where it happens that the ore lies in different 
grades of value inside the tank, the solution cannot dissolve the metalliferous 
particles in an even manner, and at the same time where it enters first it will affect 
the pulp more thoroughly, and as it goes down to the bottom will take the slimes 
forming with it, depositing them around the aperture through which the solution 
is drawn off, and even several after-leachings will not remove them. To over- 
come these drawbacks it is necessary to construct a mechanical apparatus which 
shall possess the condition of letting the soluble liquids needed to dissolve the 
metals go through the pulp in a space of time to be governed by the operator. 
Some ores are liable to contain chemical substances retarding the effectiveness of 
the soluble agent used, and where it is of great import to remove them as quickly 
as possible to keep them from going into chemical action with the solution used. 

The object of this invention, therefore, is to combine the above-mentioned 
conditions, and the apparatus can be used, in addition to other milling-plants, 
to receive the tailings direct from the mill. The filtrate can be examined in regard 
to the valuable mineral matter which may exist, giving the metallurgist the means 
of saving the valuable salts of mercury, copper, silver, gold, and the like which 
may form through the chemical or electrical action in the amalgamators where 
such are used and where the extravagant use of copper sulphate, mercury, and 
salt is in most cases the cause of the solubility of gold. 

The inventor claims: An ore-filter, comprising a funnel-shaped tank, a basket- 
pr filter-holder removably arranged in said tank and fitting closely against its 
inner wall, a filtering textile stretched over the inner surface of said basket, a top 
or hood for the tank, a shaft extended downward in the tank, and a screw mounted 
on said shaft and spaced at its inner edge therefrom, the said screw having the 
end of its upper turn turned downward. 

687920 December 3, 1901 . A. D . JANSEN. A pparatus for charging or discharging 
cyanide-vats, etc. In combination, the pair of tanks situated one above the other, 
stirring mechanism for said upper tank, having a hollow supporting or operating 
mechanism, and stirring mechanism in said lower tank, having its operating mechan- 
ism in line with the hollow mechanism of the upper tank, and means for raising 
said operating mechanism of the lower tank into said hollow mechanism of the 
upper tank. 

688085 December 3, 1901. A. G. GOLDSOBEL, W. MUTTERMILCH, and C. 
JABLCZYNSKI. Apparatus for the recovery of precious metals from photographic 
residuum. The combination with a vessel having a loose lid, a spout or outlet 
for the outflow of liquid and a conical bottom and with a precipitating material 
contained in said vessel, of a tube having a funnel-shaped end reaching within 
said vessel, and of a second tube provided with a cock connecting the aforesaid 
precipitating vessel and funnel-shaped tube with a second vessel or receiver. 


689799 December 24, 1901. R. L. GRAVES. Ore-leaching apparatus. The> 
apparatus for use in extracting ores, consisting of a plurality of tanks, a pump, 
a discharge-pipe leading from said pump and having a plurality of branches lead- 
ing to the several tanks and provided each with a discharge-pipe which may be 
turned axially or swung vertically, valves controlling the several branches, and 
a flexible supply- or suction-pipe leading to the pump and arranged to be shifted 
from tank to tank, levers connected with the several discharge-pipes whereby 
they may be turned axially, and means connected with the lower ends of the dis- 
charge-pipes whereby they may be swung vertically. 

690375 December 31, 1901, G. RUBSCH, Jr. Agitating-machine for cyaniding 
An agitating-machine for the treatment of gold and silver ore by the cyanide 
process, comprising an agitating-tank, having a conical bottom; a heating-chamber, 
surrounding the conical bottom of the agitating-tank; means to heat said chamber, 
a rotary pump, centrally disposed in the agitating-tank, adapted to take the 
solution from the bottom of the tank and discharge it above the top thereof; a 
rotary deflector, adapted to distribute the solution over a stationary deflector; 
and a stationary deflector affixed to the casing of the pump, adapted to deflect 
the solution to near the edge of the agitating-tank. 

691706 January 21, 1902. F. H. LONG. Metallurgical filter. The com- 
bination of a vessel having a conical filter-septum and an outlet-port for the filtrate 
beyond such septum, of means for establishing an end-to-end circulation of the 
vessel contents above said septum, a conical spreader and an oppositely facing 
conical baffle-plate having a projecting spiral flange successively interposed between 
the ends of the vessel and arranged adjacent to said conical filter-septum to in- 
timately direct such circulation over the surface thereof. 

697178 April 8, 1902. E. L. SHARPNECK. Apparatus for the treatment of ores. 
As a means for facilitating the dissolving of the values in ores, the combination 
of a leaching-tank, a conduit leading from and discharging directly into the tank, 
and means in the conduit connected with the heating-medium supply for agitating, 
circulating, and heating the liquid contents of the tank. 

698016 April 22, 1902. J. J. HERVEY. Cyanide-tank. Cyanide-tank having 
a tapering bottom and a central cone arranged in connection with the bottom, 
an annular lining arranged in the tank and open at its lower end, a filtering-screen, 
connecting the lower end of the lining and the central cone, the air and water- 
pipes, the charging- and discharging-pipes, and the forcing means connected with 
said pipes. 

699211 May 6, 1902. DE W. C. MOSHER. Barrel-filter. The combination 
with the lead lining of a filter-barrel, of filter-sections or plates having projections 
on their outer sides and perforations through the plates between the projections, 
and having bent ends, whereby the plates may be united to the lining by burning. 

699212 May 6, 1902. DE W. C. MOSHER. Barrel-filter. The combination 
with the lining of a filter-barrel, of perforated filter-sections, and means for support- 
ing said sections and securing them to the linings, said sections having their ad- 
jacent ends so constructed and arranged to form a longitudinal channel. 

701239 May 27, 1902. F. D. WOOD. Means for working ores by the cyanide 
process. An apparatus for treating ores consisting in combination of a plurality 
of aligned containing-tanks, a transversely concaved endless belt passing through 
and returning beneath each of said tanks, and upon which the ore is carried each 
of said belts discharging its load upon the belt of the next succeeding tank, means 
for driving said belts in unison, means by which said belts are kept transversely 
distended, and rollers disposed at intervals in said troughs and over which the 
belts pass, whereby the latter are given an undulatory movement. 

702064 June 10, 1902. F. H. LONG. Metallurgical filter. -In metallurgical 
filters, the combination with the closed perforated tank having an internal fabric- 
septum with stretcher-frame therefore to rest against the tank-walls of the feed- 
pipe leading into the tank-bottom and the separate wash-water pressure-tube 
united to said feed-pipe between the inlet and outlet valves thereof. 

702490 June 17, 1902. R. SEEM AN. ^ Apparatus for treating copper ores. A 
plant for the treatment of ores, comprising a safety vessel, a mixer revolubly 


mounted, a settler revolubly mounted at a lower level than the mixer, and a still 
revolubly mounted at a lower level than the settler, and pipes connecting the 
several vessels together, the portions of the several vessels and pipes with which 
the ammoniacal solution of copper comes in contact being of material indestructi- 
ble by such solution. 

705589 July 29, 1902. A. JAMES. Apparatus for precipitating gold and 
silver from their solutions. In the precipitation of gold and silver from cyanide 
and other solutions zinc is usually employed as a precipitant, and the use. of iron 
vessels containing the solutions has been found objectionable, because the iron 
being electronegative to zinc a galvanic action is set up between the vessel and 
the zinc, which causes the precious metal to be deposited upon the vessel instead 
of upon the precipitant. Owing to this difficulty the general practice has been 
to use vessels constructed of wood or earthenware, which are inconvenient and 
do not facilitate the cleaning-up operation. 

The object of this invention is to avoid these objections. 

To this end the invention consists in a metallurgical filter for separating precious 
metal from a solution containing it, consisting of a metallic vessel and a zinc sponge 
disposed therein, said vessel having an inner coating of enamel, whereby galvanic 
action between the metallic vessel and the zinc is prevented and deposit of precious 
metal on the vessel avoided. 

705726 July 29, 1902. J. C. WALLACE. Filter-bed. In a filter-bed, the com- 
bination of a corrugated filter-sheet or blanket having numerous perforations 
through the lower arcs of said corrugations ; a series of transverse supporting 
bars formed to fit under and receive the corrugated contour of said filter-sheet; 
a series of superimposed binding strips or bars with transverse corrugations and 
slotted ends; two longtiudinal side binding strips or bars, and bolts adapted to 
holding the several members together and in place within a filter-barrel or tank. 

706334 August 5, 1902, G. MOORE. Apparatus for leaching ores, etc. In 
dissolving the soluble portions of ores, furnace products, and other like materials 
it has always been difficult in one operation to dissolve the final traces of the soluble 
portions and at the same time completely utilize the dissolving power of the acid 
alkali. The weakening of the acid or alkali by its dissolving action makes its 
action less energetic toward the finish of the operation at the very time when the 
more difficult soluble particles needing the most energetic dissolving action are 
acted upon. This not only causes loss of reagent, but also further loss on account 
of the poor extraction of the soluble elements desired. Also, in the case of ores 
of a talcose or slimy nature the talcose portions in the form of slimes prevent per- 
colation of the solutions in tanks by clogging. These slimes should be separated 
and filtered separately by known methods. Then the remaining portion will 
easily allow percolation. 

The object of this invention is to provide an improved apparatus for the pur- 
pose of overcoming these difficulties; and with this object in view the invention 
consists, primarily, in a hollow truncated cone mounted to rotate about a cen- 
tral horizontal axial line, provided with an opening at one end to receive the mate- 
rial to be acted upon, an opening at the opposite end to receive the fluid solvent, 
means for actuating the material through the cone in one direction and means for 
actuating the fluid solvent through the cone in the opposite direction simultaneously 
with the passage of said material. 

706472 August 5, 1902. A. E. JOHNSON. Filter-bed for chlorination barrels. 
The combination with a chlorination barrel or tank of a filter-bed placed therein 
and composed of a series of bars placed side by side and having grooves in their 
sides forming spaces for filtering material, the corners of the bars being cut away 
to permit insertion of the filtering material after the bars are placed side by side, 
and binding strips located at the ends of the bars and covering the filling open- 
ings, the said strips being secured to the barrel to hold the filter in place, an out- 
let being formed in the barrel below the filter. 

708494 September 2, 1902. J. RANDALL. Apparatus for extracting metals 
from ores. In an apparatus for treating ores, the combination of a series of tanks 


with a series of agitators above said tanks and discharging into the same, so arranged 
that the overflow of the solvent fluid from each tank discharges into the agitator 
over the next adjacent tank and from thence into the latter, and means for con- 
veying the ore from the bottom of each of said tanks into the agitator directly 
above the adjacent tank for discharge into the latter. 

709135 September 16, 1902. J. BROWN. Ore-leaching apparatus. An appa- 
ratus for leaching ores, comprising a tank adapted to contain water or other liquid, 
a conduit connected to and extending upwardly from the tank and having the 
plurality of chambers, a hopper disposed above the upper chamber, ball-valves 
for controlling the discharges of the chambers and hoppers, electromagnets dis- 
posed above the valves and adapted when energized to raise the same, the hoods 
and deflectors arranged in the chambers and hopper above the electromagnets, 
an electrogenerator, a movable commutator and circuit wires connecting the 
magnets, generator and commutator, the said commutator being adapted to change 
the circuits and the condition of the magnets. 

709593 September 23, 1902. D. C. BOLEY. Apparatus for treating pulverized 
ores of gold and silver. The difficulty which has been experienced in treating finely 
divided ores by filtration with a cyanide solution is well known. In the case of 
battery slimes, which are produced by crushing the ore in the battery in the pres- 
ence of either water or a cyanide solution, and equally in the case of the fine dust 
which is produced by dry crushing and which becomes a slime by the addition 
of moisture, the difficulty in all these arises when attempt is made to filter the 
material, so as to draw off the moisture, because the slimes collect upon the sur- 
face of the filter, and when this collection reaches a certain thickness the fluid 
will no longer pass through and the filtering surface must then be cleaned, and 
this difficulty begins very soon and constantly increases as the filtering "proceeds. 
Attempt has been made to overcome this to some extent by producing a vacuum 
at the delivery side of the filter, and also an attempt to facilitate the filtration 
by creating an air pressure on the other side of the filter; and it has been attempted 
to prevent the collection of this impervious coating of filtrates by stirring and 
agitating the contents of the filter. So far there has been no organized apparatus 
capable of carrying on this work of filtering slimes successfully and economically, 
and such an organized apparatus is the object of the present invention, which 
consists in a revolving filter cylinder having vacuum chambers and means for 
supplying air pressure, the filtering surface being arranged in cylindrical form 
inside of the vacuum chambers, and the mode of operation being to agitate the 
pulverized ore by revolving the cylinder and by the pressure of compressed air, 
and dissolving the gold and the silver in the presence of a solution of potassium 
cyanide and of the oxygen derived from the compressed air, and the removal of 
the solution containing the gold and silver by filtration, assisted by the vacuum, 
and the continuous removal of the filtrates from the surface of the filter by their 
own gravity in the turning of the cylinder, and the further cleaning of the filter 
surface by a backward blast of compressed air applied after the filtering there- 
through ceases. 

710462 October 7, 1902. R. D. JACKSON. Settling-tank. In a settling-tank, 
a distributer having downwardly extending discharge outlets for pulp and liquid, <?>6 
means for supplying material to said distributer, means for rotating said distributer, 
and means for raising said distributer while rotating, whereby the distributer 
rises steadily above the accumulating deposit. 

710495 October 7, 1902. S. T. MUFFLY. Apparatus for treating ores. An 
apparatus for treating ores, comprising a rotary cylinder, air-inlet and outlet pipes 
connected therewith at opposite ends thereof, automatic valves oppositely directed 
and controlling the inlet and outlet pipes, means for forcing air through the said 
inlet pipe, means for heating the said air, a solvent container connected with the 
air-inlet pipe whereby the solvent is forced by and with the air into the rotary 
cylinder in the form of a spray, means for governing the amount and pressure of 
air and of the solvent, devices within the cylinder for scattering and agitating 
the ores as the said cylinder is revolved. 

711236 October 14, 1902. H. SMITH and P. C. BROWN. Apparatus for use 
in extracting precious metals from their ores. In a lixiviation apparatus, a revoluble- 


tank, pipes conducting a solvent air, and steam to the tank, means for rotating 
the tank, and a pipe in the end of the tank opposite the end containing the supply- 

712963 November 4, 1902. J. J. PRINDLE. Barrel-filter. In a chlorination 
barrel-filter, a platform comprising a series of perforated members or sections 
having the end portions thereof thickened or enlarged, said enlarged portions 
provided on their lower sides with prolonged curved faces forming supporting 
heels which conform to the curvature of the barrel in which the filter-platform 
is adapted to be used, and bolts passing through said curved heels and co-operating 
therewith in holding the platform in place. 

713694 November 18, 1902 J. P. SCHUCH, Jr. Ore-mixing-machine. An ore- 
mixing-machine, comprising the following elements: An ore-mixing-tank, a false 
bottom including a strainer, means for discharging air beneath the strainer to 
keep the meshes thereof free from any accumulation of slime or the like, air supply- 
pipes disposed above the strainer to effect aeration of the contents of the tank, 
a track carried by the upper outer portion of the tank, an agitator-shaft having 
its upper portion polygonal in cross-section, a spider having a hub engaging the 
said polygonal portion and carrying traveler-wheels at its extremities to engage 
'the track, agitator-bars suspended from the spider, and beaters or stirrers carried 
by the bars, each set of beaters being disposed in break-joint order with relation 
to the adjacent set of beaters. 

714822 December 2, 1902. J. RANDALL. Settling-tank or decanting vessel. A 
settling-tank, consisting of a body having a vertical side and a bottom formed 
of slopes of different inclinations and provided with a central outlet, the said side 
having a cutaway portion forming an overflow lip, a launder encircling said lip 
and provided with a discharge-spout, a baffle-plate of cylindrical form connected 
by strips to the upper portion of said side and extending into the tank below the 
top and nearly to the lower edge of said side, and a pipe leading from said central 

718680 January 20,' 1903. B. TULLY. Barrel-filter. A filter, comprising a 
rotatable barrel, provided with a lead lining, the body of the barrel being pro- 
vided with apertures and the lining being perforated opposite said apertures, a 
lead launder arranged on the exterior of the barrel and provided with a plurality 
of lead branch pipes, said branch pipes at their inner ends being fitted in said aper- 
tures and connected to the lead lining about said perforations. 

719273 January 27, 1903. Z. B. STUART. Apparatus for treating ores. A 
tank having an open top and a concave bottom formed of .perforated removable 
plates, a removable, conical plate upwardly projecting from the center of the bot- 
tom, a perforated box under said conical plate, a layer of coarse fabric surround- 
ing said perforated box, a filtering material under said perforated plates, a pump, 
a suction-pipe extending from said pump to and through the mixture in said tank 
to a point adjacent to the upper surface of the mixture, and a discharge -pipe extend- 
ing from said pump to a point adjacent to the conical part in said tank, a vacuum- 
tank, a pipe connecting said vacuum-tank to said perforated box, and a suction- 
pump connected to said vacuum-tank. 

719664 February 3, 1903. J. B. HEFFERNAN. Chlorination barrel In a 
chlorination barrel a parallel series of pipes having numerous small orifices through 
their longitudinal walls, one or more headers adapted to receiving the ends of 
said pipes, a valve or valves connecting said header or headers with an outside 
source of fluid pressure. 

719756 February 3, 1903. S. C. C. CURRIE. Mechanism for mixing and stor- 
ing liquids and gases for ore treatment. In combination, an alkali mixing-tank, 
an alkali stock-tank at a lower level and connected by a pipe thereto, a mixing- 
chamber at a level below the alkaline storage-tank, safd mixing-chamber having 
inclines leading from opposite sides, a chlorine gas supply-pipe leading from above 
the top of the mixing-chamber into the bottom thereof, a storage-tank for chlor- 
inated liquid below the level of the mixing-tank, and a gas supply-pipe leading 
from the top of the mixing-chamber nearly to the bottom of the storage-tank. 


722314 March 10, 1903. L. H. MITCHELL. -Discharge means for tanks. A 
discharge apparatus for tanks, provided with a casting having an upwardly pro- 
jecting rim provided with shoulders having longitudinally inclined under faces, 
a funnel having a base provided with a depending offset portion, a gasket mounted 
in the recess formed by said offset portion and adapted to seat upon the top of 
the rim, lugs formed on the depending portion and provided with longitudinally 
curved upper faces to engage the inclined faces of the shoulders, and operating 
handles at the top of the funnel. 

722399 March 10, 1903. H. R. CASSEL. Barrel-filter A barrel-filter com- 
posed of a barrel having a lead lining, and of a filter having rigid cores and sur- 
rounding lead casings made integral with the lining. 

7255Jt9 April 14, 1903. H. R. ELLIS. Centrifugal lixiviating-machine. In a 
centrifugal filtering-machine, the combination of a rotary-shaft, a drum mounted 
thereon, a perforated partition within the drum, arranged concentrically with 
the periphery of the drum at such distance therefrom as to form an annular chamber <y 
about the perforated partition, means for supplying liquid to the annular chamber, V>< 
a discharge opening in the bottom of the drum, a cover therefor adapted to be 
held open by centrifugal force when the drum is rapidly rotated to permit dis- 
charge of the charged liquid, and to be held in closed position when the drum is 
rotated slowly, and a discharge-gate in the bottom of the drum at a point nearer 
the center than the discharge opening. 

727230 Maij 5, 1903. F. G. UNDERWOOD. Leaching-tank filter. The appa- 
ratus consists of a tank having a central discharge aperture provided with a mov- 
able closure, an interior filter diaphragm spaced from the bottom of the tank and 
having a central discharge aperture registering with the tank-discharge aperture 
and provided with a movable closure, in combination with vertical filter members 
radially disposed and spaced apart between said discharge apertures and the walls 
of the tank and communicating with the space beneath the diaphragm. 

727362 May 5, 1903. H. HIRSCHING. Apparatus for treating ores. An ore- 
treating apparatus including a leaching vessel, a settler, a filter, a still, a condenser 
containing a coil, a stock-solution-tank, and an absorption-tank, said absorption- 
tank consisting of an outer casing communicating with a cooling-water-tank, an \, 
inner casing spaced from the outer casing and communicating with the stock- "Vv / 
solution tank, and an innermost casing spaced from the inner casing and com- < 
municating with the coil of the condenser, whereby the vapors and fluid emerging 
from the coil, are caused to flow through the innermost casing and through the 
absorption water, and the absorption water is caused to flow through the inner 
casing to the stock-solution-tank, said parts being connected together by means 
of pipes. 

728126 May 12, 1903. P. W. MCCAFFREY. Precipitating apparatus. In pre- 
cipitating apparatus, the combination of a tank having curved walls, said tank 
being adapted to hold the solution to be treated and being provided with a central 
partition around the extremities of which the liquid is free to circulate, blocks or 
pieces made fast to the opposite sides of the tank, their inner surfaces being parallel 
with the surfaces of the partition, and cylinders mounted to rotate on opposite 
sides of the partition and partially immersed in the solution, said cylinders being 
perforated and containing scrap iron, the ends of the cylinders being located as 
cloee to the partition and the said blocks as is practicable in order to allow perfect 
freedom of movement, and means for rotating the cylinders in reverse directions 
whereby the .liquid is set in motion in a circular current. 

728746 May 19, 1903. P, W. MCCAFFREY. Means for precipitating dissolved 
metals. In precipitating means, the combination of a tank adapted to hold the 
liquor from which the precipitation is to be made, a number of perforated cylinders 
containing scrap metal, said cylinders being mounted to rotate in said tank which 
is constructed to receive solution at one end and discharge it at the opposite end 
above the lowest part of the cylinders, the latter being arranged in successive 
order from the feed to the discharge extremity of the tank and partially immersed 
in the solution, and suitable means for producing a current of liquid through the 
tank from end to end, whereby the contact of the liquid with the scrap metal in 
the tanks is facilitated 


729805 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Apparatus for ex- 
tracting metals from ores. In an apparatus for extracting precious metals from 
their ores, the combination of a tank for containing a cyanide or other suitable 
solution, means for reducing ore to a finely divided or comminuted state, one or 
more conduits connected with the solution-tank and arranged to supply the ore 
with solution incident to the reduction thereof, means for agitating and mixing 
the ore and solution, arranged to receive the same from the reduction means, a 
filter arranged to receive the ore and solution from the agitating and mixing means, 
and adapted to separate the solution from the ore, one or more decant ing-tanks' 
arranged to receive the solution or solutions from the filter, a precipitaling-tank 
which receives the clear solution from the decanting-tank or tanks, and means for 
transferring the solution from the precipitating-tank back to the solution-tank. 

729806 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Agitation-tank. 
The combination of a tank, a central, vertical, cylinder arranged therein, a piston 
movable in the cylinder and having a rod extending through the upper head thereof, 
a gear disposed above the tank and adapted to be connected by a driving connec- 
tion with a motor, a shaft stepped on the piston-rod and keyed to and adapted 
to move vertically through the gear, wings connected to and extending inwardly 
from the vertical wall of the tank, agitating means carried by the said shaft and 
surrounding the upper end of the cylinder, and comprising a head fixed on the 
shaft, blades disposed below the wings and connected together, said blades being 
curved in the direction of their length and inclined in the direction of their width, 
connections between the outer portions of the blades and the head of the shaft, 
connections between the inner portions of the blades and said shaft, and a pipe 
communicating with the cylinder below the piston and adapted to be connected 
with a source of fluid-pressure supply. 

730195 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Metallurgical filter 
In an apparatus for extracting precious metals from their ores, the combination 
of a filter comprising a frame, an endless filter-cloth, means for driving same, means 
for pressing pulp against the upper stretch of the cloth at different points and 
separate receptacles arranged below the cloth at such points, and a decanting- 
vat having separate tanks connected with the said separate receptacles of the 
filter; the said separate tanks communicating with the vat at their upper ends, 
and having valved discharges at their lower ends. 

730384 June 9, 1903. W, H. HOTTER, Agitating apparatus. The combina- 
tion of a rocking platform, means for operating the same, a frame mounted to 
reciprocate adjacent to the platform, cylindrical tanks or vats trunnioned on the 
frame and engaging the platform, flexible devices connected with the opposite 
extremities of the frame, guides therefor, a liquid containing-tank, a piston therein, 
stems protruding from the opposite extremities of the tank, and a valve-controlled 
conduit connecting the opposite extremities of the tank, the flexible devices of the 
frame being connected with the piston stems. 

730385 June 9, 1903. P. W. MCCAFFREY. Apparatus for the precipitation of 
metals from solutions. In apparatus for the precipitation of dissolved metallic 
values, the combination of a tank adapted to hold the solution to be treated, and 
a perforated receptacle containing scrap metal, the perforated walls of the said 
receptacle being composed entirely of the same material, said receptacle being 
partially immersed in said solution and mounted to rotate therein, wherehv the 
solution is mads to circulate through the scrap metal for the purpose set forth. 

732720 July 7, 1903. H. DUNCAN and R. R. SHERRIFF. Apparatus for sepa- 
rating liquids from solids. A machine for separating liquids from solids, com- 
prising in combination a framing and gear, carrying and traversing an endless 
band of filter-cloth, automatic slip devices for securing the band, a vacuum-box 
or suction-chamber located upon the under surface of said band, and an interposed 
endless band of wire cloth or gauze arranged to support and travel with the filter- 

733739 July 14, 1903. F. H. OFFICER, R. H. OFFICER, J. H. BURFEIND, and 
J. W. NEIL. Apparatus for use in metallurgical processes. In an apparatus for 
treating ores or other materials containing gold or silver or other metals by the 


cyanide process, the combination of a treating-tank, an absorption-tank containing 
a caustic solution, a compressor and connections as described between the com- 
pressor, treating-tank and absorption-tank whereby air or gas under pressure 
may be forced from the compressor through the material in the treating-tank and 
tiie gases released or freed from said material may be passed through the absorbing 
solution in the regenerator-tank and thence to the compressor, so as to permit 
the air to be used over and over and the valuable products released in the treating- 
tank to be recovered, as and for the purpose described. 

735206 August 4, 1903. L. P. BURROWS. Mixing and dissolving apparatus. 
A mixing and dissolving apparatus, comprising a containing vessel, a shaft in 
and movable relatively to said vessel, an inner and an outer set of stirring-plates 
carried by and arranged around and substantially parallel to said shaft, the ad- 
jacent plates of the inner and outer sets converging toward each other from their 
front to their rear edges, and stirring-blades secured to the rear edges of said 
plates and arranged in a spiral line around the shaft, the corresponding blades 
of the outer and inner sets being twisted in opposite directions. 

735834 August 11, 1903. L. B. SKINNER. Filter. A filter-bar, consisting of 
a body portion and separated tongues projecting laterally therefrom and recessed 
for the passage of filtering fluid, each tongue with a beveled end, and beveled faces 
on the body between the tongues. 

735835 August 11, 1903. L. B. SKINNER. Filter. The combination in a 
filter-bed, of bars having each a body portion and a perforated side flange with 
a beveled edge, and a beveled face constituting the bearing of the flange of the 
adjacent bar. 

735960 August 11, 1903. G. S. FOSTER and S. S. D. STRINGER. Metal-extract- 
ing and ore-lixiviating apparatus. The combination of a solution-supply tank, 
a series of intercommunicating leaching-tanks adapted to receive solution from 
said supply-tank, drain-pipes leading from said leaching-tanks, a launder into 
which said drain-pipes are arranged to discharge, and a charcoal box connected 
to said launder, 

736036 August 11, 1903. H. L. SULMAN and H. F. KIRKPATRICK-PICARD. 
Apparatus for the recovery of precious metals. In an apparatus for recovering 
precious metals, the combination of a conical vessel having an inner amalgamated 
copper surface, a conical body having an outer amalgamated copper surface dis- 
posed concentrically within the vessel and forming therewith a narrow interspace, 
a body of mercury charged with an electropositive metal in the interspace, an 
electrolytic vessel for charging the mercury, a mercury-pump, an inlet conduit to 
the top of the interspace from the electrolytic vessel, an outlet conduit for mercury 
from the bottom of the interspace to the pump, a conduit from the pump to the 
electrolytic vessel, an inlet conduit at the bottom of the vessel for the solution 
carrying the values, a non-return valve in said conduit, means for forcing the 
solution up through the interspace, and a launder at the top of the vessel to receive 
the discharged solution. 

736078 August 11, 1903. H. T. DURANT. Apparatus for the treatment cf ores 
with solvents. A device for the treatment of ore, tailings, or other material by 
solvents, consisting of a tank having a conical bottom, a plug in said bottom and 
made conical to correspond to the angular walls thereof, a pump or forcing device 
discharging into the apex of the cone, and a return connection between the upper- 
part of the tank and the suction of the pipe. 

736597 August 18, 1903. C. D. GROVE. Barrel-filter. In a barrel-strainer,, 
the combination with the shell thereof of a strainer the exterior surface of 
which^ is in contact with the barrel, its inner surface being provided with suitable 
straining perforations in the form of slits combined with transverse grooves beneath 
the interior surface and establishing communication between said slits and the: 
discharge opening. 

737046 August 25, 1903. J. B. TRUITT, W. L. TRUITT, and W. O. TEMPLE.. 
Precipitating zinc box. In a precipitating; zinc box, the combination of an outer 
imperforate box having a valved outlet in its bottom and a valved outlet above 


its bottom, a launder at each outlet, and an inner removable zinc-holding box 
having a perforated bottom, and supported in the outer box above the bottom 
of the latter. 

737533 August 25, 1903. E. L. V. NAILLEN. Apparatus for extracting gold 
and other metals from ores. In an apparatus for extracting metals from ores, the 
combination of a concentrating-tank consisting of two cone-shaped sections secured 
together at their largest diameter by means of suitable flanges and provided with 
an intermediate strip secured between said flanges and projecting outwardly, 
a settling-tank disposed around the concentrating-tank, a perforated diaphragm 
placed between the concentrating- and settling-tanks and supported upon said 
intermediate strip, and a suitable bracket bolted to the settling-tank and adapted 
to form two horizontal sections within the settling-tank. 

738148 September 8, 1903. J. B. DE ALZUGARAY and W. A. MERCER. Appa- 
ratus for extraction of precious metals from their ores. Apparatus for treating ores, 
consisting of a closed containing vessel or vat provided with fixed internal blades 
or wings, a rotating hollow spindle provided with ball-bearings and having hollow 
blades or beaters set at an angle, means for raising and lowering the spindle in 
the vat, gearing for rotating the spindle, and means connected with the vat for 
supporting the gearing and steadying the spindle, all combined, arranged, and 
operating as shown and described and for the purpose set forth. 

738329 September 8, 1903. W. E. HOLDERMAN. Device for treating slimes. 
In a device for treating slimes having a liquid-tight case, a discharge-pipe pro- 
vided with a valve in its bottom, an inclined floor in said case, spaced bars on 
said floor and the sides of the case, a filtering fabric covering said bars and over- 
lapping the upper edge of the tank, a molding to hold the fabric in operative posi- 
tion, and pipes provided with stoppers leading from the filter out through said 

740193 September 29, 1903. E. D. SLOAN. Barrel-filter. In a barrel-filter", 
the combination with the barrel of a partial lining of porous filter-blocks fitting 
closely together and having grooves formed on their under sides which intercon- 
nect from block to block and form drain channels; means for sealing said draining 
channels from the inner space of the barrel, and a discharge port leading from 
the drains out of the barrel. 

74.1189 October 13, 1903. H. H. THOMPSON. Apparatus for extracting precious 
metals. An apparatus for extracting precious metals, comprising a receptacle 
provided with an outlet, a series of bodily movable and loosely mounted agitating 
.arms gradually decreasing in length and adapted to be retained in their operative 
position when rotated in one direction and to assume an inoperative position when 
moved in an opposite direction, a rotatable means for suspending said arms within 
said receptacle, said rotatable means and arms bodily movable, a series of screened 
nozzles communicating with said receptacle, means for supplying a cyanide solu- 
tion, compressed air and water to each of said nozzles either separately or in any 
preferred combination, operating means for said rotatable means, and means 
communicating with said supply means and the said outlet for exhausting the 
solution from said receptacle. 

741402 October 13, 1903. W. E. HOLDERMAN. Leaching-tank. In a filtering- 
tank having vertical slats covered with a filtering fabric, a filtering partition extended 
across said tank, a trough in its bottom for the filtrate, and an orifice through 
the filtering fabric of said tank into which the filtrate from said trough is dis- 

741499 October 13, 1903. A. E. JOHNSON. Barrel-filter. In a barrel-filter, 
the combination with a suitable barrel or cylinder, of a filter having a perforated 
bottom, side walls extending below the bottom and engaging the barrel on the 
inside, filtering material resting on the bottom and confined by the side walls, a 
top perforated plate, and suitable means for securing the filter in place, a channel 
being formed underneath the bottom of the filter to receive the filtered liquid, 
the barrel being provided with a valved outlet in communication with the said 


743550 November 10, 1903. J. A. OGDEN. Process of extracting metals from 
cyanide solutions. The process of treating gold, silver, or other metals from a 
cyanide or primary solution, consisting in mixing in a receptacle a given quantity 
of said primary solution with a given quantity of a secondary solution having 
a metal base and capable of liberating the metals in said primary solution; leaving 
said mixture in said vessel until said liberation is partially effected, then passing 
said mixture into a second receptacle and agitated therein so as to produce a com- 
plete commingling of said solutions, from thence running the mixed solution into 
a settling-tank and allowing it to settle, drawing off the clear solution, and then 
drying the precipitation and pressing and melting it into bullion. 

743551 November 10, 1903. J. A. OGDEN. Apparatus for extracting precious 
metals from cyanide solutions. An apparatus for the purpose set forth, consisting 
of primary and secondary solution-tanks, each provided with discharge-pipes with 
controlling-cocks, and measuring-glasses; a mixing vessel adapted to receive the 
flow from said measuring-glasses; a barrel with rotatable blades therein and 
having a glass gauge on the outer face thereof, and a settling-tank adapted to 
receive the discharge from said barrel. 

745472 December 1, 1903. W. H. ADAMS, Jr. Apparatus for treating ores. 
The combination of a tank, a box, a pipe at the top of the tank connecting the 
same with the box, a pump connected with the box, and nozzles connected with 
the pump and arranged to discharge liquid into the tank at intervals tangen- 
tially in an approximately horizontal plane. 

746867 December 15, 1903. DE W. C. MOSHER. Chlorination barrel A 
chlorinating barrel provided with a resistant lining and with an arched channeled 
rib extending longitudinally, secured to said lining and having perforations between 
the interior -of the rib and barrel, and a discharge opening communicating with 
the interior of the rib. 

748088 December 29,^ 1903. G. MOORE. Filtering system. In a filtering sys- 
tem, the combination with a tank for containing the material to be filtered and 
a cleansing-fluid tank, of a filter, means for introducing and removing the same 
into and from each of said tanks alternately, means for drawing the contents of 
said tanks through the filter, and means for cleansing the filter. 

748217 December 29, 1903. C. H. RIDER. Apparatus for dissolving organic or 
inorganic substances. A device consisting of an acid-tank, a water-tank, an upper 
series of tanks connected with the acid-tank and the water-tank and to each other, 
a lower series of tanks adapted to receive the substance to be treated, connected 
to the upper series of tanks and to the water-tank and to each other; a retort, 
means for heating the retort, a pipe passing from the retort through the lower 
series of tanks, and a condenser into which the last-named pipe extends, substan- 
tially as and for the purposes specified. 

748462 December 29, 1903. W. J. ARMBRUSTER. Chlorination barrel. A 
chlorination barrel having a pulp-chamber and a chlorine generating compart- 
ment rotatable therewith, a wall separating the pulp-chamber from the compart- 
ment, said wall having an unobstructed opening disposed about the axis of rota- 
tion of the barrel for freely permitting the discharge of the chlorine above the 
surface of the pulp in the pulp-chamber. 




323222 July 28, 1885. J. W. SIMPSON. Process of extracting gold, silver, 
and copper from their ores. The ore is crushed to a powder, treated with a solu- 
tion produced by dissolving 1 pound of cyanide of potassium, 1 ounce of carbon- 
ate of ammonia, and ounce of chloride of sodium in 16 quarts of water when 
the ore contains gold and copper only; but when it is rich in silver the quantity 
of chloride of sodium employed is increased. After thorough agitation of the 
ore in the solution the mixture is allowed to stand until the solution has become 


clear, when the dissolved metals are precipitated out by means of a plate of zinc 
suspended in the liquid. The metal is precipitated upon the zinc and can be 
removed by scraping or by dissolving the zinc in sulphuric or hydrochloric acid. 

403202 May 14, 1889. J. S. MACARTHUR, R. W. and WM. FORREST. Process 
of obtaining gold and silver from ores. The invention consists in subjecting 
finely-powdered argentiferous ores to the action of a solution containing a small 
quantity of a cyanide, the cyanide contents of the latter being proportioned to 
the quantity of gold or silver, or both, found, by assaying or otherwise, to be in 
the ore. Any cyanide soluble in water may be used, but in all cases the solution 
must be extremely dilute, since such a solution has a selective action in dissolving 
gold or silver in preference to the baser metals. The claim covers the use " of a 
cyanide solution containing cyanogen in the proportion not exceeding 8 parts 
of cyanogen to 1000 parts of water." 

41 8 137 December 24, 1889. J. S. MACARTHUR, R. W. and WM. FORREST. 
Process of separating gold and silver from ore. This invention has for its object 
the preventing of loss of cyanide in the care of weathered ores by first neutraliz- 
ing the ore with an alkali or alkaline earth and then leaching such prepared charge 
with a cyanide solution. Further, the precious metal thus dissolved in the cyanide 
solution is precipitated out by passage through a sponge of zinc composed 
of fine threads or filaments of zinc formed by cutting shavings with a turning tool 
from a series of zinc disks held in a lathe, or by passing molten zinc at a tempera- 
ture just above the melting-point through a fine sieve and allowing it to fall into 

482577 September 13, 1892. E. D. KENDALL. Composition of matter for the 
extraction of gold and silver from ores. Consists in extracting gold and silver from 
minerals, " tailings," and other matters containing one or both of these metals 
by an aqueous solution of one or more soluble ferricyanides and one or more soluble 
cyanides prepared by dissolving a ferrocyanide in one portion of water and a cyanide 
in another portion and mixing the two solutions, or by adding either salt in solid 
form to the solution of the other. 

492221 February 21, 1893. C. MOLDENHAUER. Extracting gold from its ores. 
Consists in subjecting gold ores to the solvent action of cyanide of potassium in 
the presence of ferricyanide of potassium. 

494054 March 21, 1893. W. A. G. BIRKIN, Process of and solvent for sepa- 
rating precious metals from their ores. Covers the art of separating metals from 
their ores by subjecting the suitable comminuted ore to the action of a menstruum 
composed of potassium cyanide, potassium ferricyanide, and peroxide of hydrogen 
in water, and separating the values from this solution by precipitation, deposition, 
or electrolysis. 

496950 May 9, 1893. H. PARKES and J. C. MONTGOMERIE. Process of extract- 
ing gold or silver. Claims a process for extracting gold and silver from ores or 
compounds by an interrupted operation, consisting of treating the ore with cyanide 
of potassium in the presence of oxygen under pressure with agitation, the ore 
being subsequently filtered and washed and the precious metals recovered from 
the liquor by precipitation or other known means. 

514^57 February 6, 1894- W. P. MILLER. Process of recovering precious 
metals. Has for its object the preservation of the cyanide solution, and consists 
in the treatment of the ore with the cyanide solution in air-tight vessels not only 
during the process of solution, but during the filtration and up to' the time of the 
precipitation of the precious metals from the filtered solution. 

622739 July 10, 1894. C. MOLDENHAUER. Process of precipitating gold or 
other precious metals from their solutions Dissolves gold and other precious metals 
from their ores by means of acid-cyanide solutions, which consist in treating the 
solution with aluminum, so as to precipitate the gold from the solution, and then 
add a free alkali or alkaline earth for a regenerating solution. 

524601 August 14, 1894. J- C. MONTGOMERIE. Process of extracting gold 
or silver from ores. Sodium oxide (caustic soda) or other suitable oxide of the 
alkalies is added to the cyanide solution before mixing the same with the ore. 


After the precious metals have been dissolved in the solution and the liquid filtered 
off and the precious metals precipitated out, the remaining solution is tested to 
determine the quantities of potassium and sodium oxide still remaining in it, and 
any deficiency is supplied or the solution fortified by the addition of the necessary 
quantity of these agents, so as to restore the solvent solution to its original char- 
acter and strength. 

524690 August 14, 1894, E. D. KENDALL. Method of treating gold or silver 
ores. Covers the treating of gold or silver ores with a composition of matter con- 
sisting of sodium dioxide and a suitable cyanide in solution. / 

532238 January 8, 1895. C. MOLEENHAUER. Method of precipitating precious ' * 
metals from solutions. Consists in subjecting the ores to the action of an acid- ^ *j 
cyanide solution so as to dissolve the gold or other precious metal" contained in J 
them, then adding aluminum so as to precipitate the gold or other metal from 
the solution, and then regenerating the cyanide solution by means of a free alkali 
or alkaline earth. 

532895 January 22, 1895. J. C. MONTGOMERIE. Process of extracting gold 
or silver from ores. Consists in adding an oxide or one of the alkaline bases to a 
cyanide solution, then mixing with the ore or compound the solution thus rendered 
alkaline, then conducting the process under pressure of oxygen, and afterwards 
separating from the ore the liquid containing the gold and silver in solution, then 
treating that liquid in any approved way for the recovery of the precious metal, 

538951 May 7, 1895. S. C. CLARK. Process of treating refractory ores. Claims 
the process of treating a refractory ore, consisting essentially in boiling the ore I 
in water containing from 10 to 15 pounds of cyanide of potassium to each ton 
of ore for about one hour or for a sufficient length of time to enable the cyanide 
of potassium to dissolve the chloride, sulphide, or bromide in the ore, then allow- 
ing the solution to settle and finally evaporating the clear liquid so as to obtain; 
a residue containing metal. 

540359 June 4) 1895. G. KENNAN. Process of and apparatus for treating 
ores. Claims the process of treating the ores of gold and silver, consisting in sub- 
jecting the same to the action of cyanide of potassium, agitating the same for a 
short period of time, discontinuing the agitation, and bringing air in contact there- 
with, the oxygen thereof increasing the action of the cyanide, continuing the agita- 
tion for a few minutes, until every particle of ore has been brought in contact 
with the cyanide solution in the presence of atmospheric air, and withdrawing 
the solution from the remaining pulp or ore. 

541333 June 18, 1895. F. RINDER. Process of separating gold and silver. 
Consists in the treatment of cyanide solutions containing gold and silver with ^/ 
sulphide of iron to precipitate the silver and then with chloride of zinc to pre- /\. 
cipitate the gold. 

543543 July 80, 1895. M. E. WALDSTEIN. Process of extracting gold or 
silver from ores. Consists in subjecting the ores to the action of cyanide of potas- 
shim, adding to the material during this action a salt or salts (such as bin oxide 1 
of barium) decomposable by an acid and yielding oxygen, and sufficient acid to ' 
decompose this salt or salts, and subsequently adding an excessive acid to decom- 
pose the soluble cyanide and finally separating the precious metals as sulphides 
by precipitation with sulphureted hydrogen or by a soluble sulphide. 

543782 July 30, 1895. M. CRAWFORD. Process of extracting precious metals 
from their ores, Consists first in lixiviating the ores of the precious metals with a 
cyanide solution to which has been added a substantially neutral substance which 
contains a permanent excess of oxygen; second, in subjecting the gangue and 
accompanying cyanide solution to an amalgamating process; and, thirdly, in 
withdrawing the solution from the tailings, and extracting the precious metuls 
therefrom. The neutral substance containing a permanent excess of oxygen may 
be prepared by mixing peroxide of sodium with dilute sulphuric acid and neu- 
tralizing with silicate of soda. 

543676 July 30, 1895, M. CRAWFORD. Process of extracting precious metals 
from their ores. Consists in, first, lixiviating the ore with a cyanide solution to 


which has been added a small quantity of a substance prepared by agitating ether 
with binoxide of barium and adding thereto small quantities of very dilute hyciro- 
chloric acid, and neutralizing by silicate of soda, and, second, separating the precious 
.metal fiom this solution in which the ore has been lixiviated. 

545852 September 8, 1895. P. DE WILDE. Method of extracting gold. The 
precipitation of gold in the iorm of a mixture of aurous cyanide and cuprous cyanide 
by acidulating a cyanide solution containing the gold with an acid sulphurous 
compound and afterwards adding a solution of copper salt. Also, specifications 
provide for the dissolving of gold by the use of a weak solution of potassium or 
sodium cyanide which has been in contact with the minimum or protoxide of lead, 
and for the recovery and utilization of the spent cyanide by its conversion to Prus- 
sian blue. 

547790 -October 15, 1895. J. J. HOOD. Extracting metals. The method for 
the extraction of precious metals from their ores, which consists in treating the 
ore with a solution containing both a cyanide of potassium or sodium and a salt 
or compound of a baser metal in the proportion of one part at least of the former 
to two parts of the latter; the metallic base of the solution being displaced by 
the precious metal, the former being precipitated. The gold is then precipitated 
out by a copper-zinc couple. By " baser metal " is meant mercury, lead, and 
such other metals as are displaced by metallic gold from their solutions in alka- 
line cyanides A mixture that answers well consists of two parts, by weight, of 
cyanide of potassium (or its equivalent of cyanide of sodium), one part of mer- 
curic chloride or its equivalent of sulphate or other mercury salt, and from one- 
half to two parts of caustic soda. 

549736 November 12, 1895. J, C. MONTGOMERIE. Extraction of gold and 
.silver from ores. The improved process of extracting gold and silver from ores 
or compounds containing the same, consisting in treating the ore in a vessel con- 
taining water with a cyanide, an alkaline oxide, a nitrate, and an oxidizing agent. 
.Sodium dioxide may be taken as a representative of the alkaline oxide and aid 
under pressure as an oxidizing agent, as set forth in this claim. 

555463 February 25, 1896. J. S. MACARTHUR and C. J, ELLIS. Process of 
^extracting gold and silver from ores: Consists in subjecting the ore to the action 
of a cyanide solution and precipitating, by means of a metallic compound capable 
of combining with sulphur any sulphur which may become soluble in the solution 
and thereby rendering it inert. Salts or compounds of lead, manganese, zinc, 
mercury, and iron are types of the metallic compound employed. By means 
of a salt of lead any copper present in the cyanide solution may be precipitated 

555483 February 25, 1896. T. L. WISWALL and J. B. FRANK. Process of 
recovering precious metals from solutions. The process of extracting precious metals 
from solutions by causing said solutions to flow through a precipitating alloy, 
subdivided into a mass of hardened filaments, and composed of zinc, lead, and 
one or more other metals which impart to said filaments a tensile strength suffi- 
cient to withstand the compression of the flowing solution, such as arsenic, anti- 
mony, cadmium, or bismuth, and in which alloy there is present not more than 
97 per cent, of zinc. 

576173 February 2, 1897. H. L. SULMAN. Process of precipitating precious 
metals from their solutions. Consists in purifying zinc fumes or dust of oxides 
by intimately mixing with the same an ammoniacal substance, and then mixing 
a quantity of said fumes or dust so purified with the solution. The apparatus 
by which to perform the process and for the treatment of the ores is also claimed. 

578089 March 2, 1897. J. F. WEBB. Process of extracting gold and silver 
from ores. The process or method for the extraction of gold and silver from their 
crushed ores, consisting in saturating the ores in a solvent solution of potassium 
cyanide, then applying a current of compressed air from beneath and maintaining 
the same throughout the leaching process, then shutting off the current, then 
applying a current of compressed air on top of the solution after the ore-contain- 
ing Vat has been closed at top and a drain at the bottom has been opened, and 
maintaining the same until the solution has been driven out of the ore, then shut- 
.ting off the current of air, then admitting water to the vat, then introducing a 


compressed-air current at the bottom of the vat, and finally introducing a cur- 
rent of compressed air on top after the vat has been again closed at top and a- 
drain opened at bottom. 

578178 March 2, 1897, D. WHITE and T. M. SIMPSON. Process of and appa- 
ratus for extracting precious metals from slimes, etc. In the extracting of precious 
metals from slimes and other auriierous and argentiferous materials, the process 
which consists in mixing the said material with a cyanide solution in a closed vusel,. 
then agitating the mixture by passing a gas under pressure through tLe s.Lrr.e, 
then passing "gas under pressure, together with the gases arising from tLe acilon 
of the cyanide solution in the said material, through another quantity oi stud 
material and cyanide solution in a closed vessel, then conveying the gases Lack 
to the source of compression and drawing off the solution, containing the precious 
metal and extracting said metal. The apparatus for accomplishing this purpose 
is also claimed. 

578340 March 9, 1897. W. A. KONEMAN. Process of extracting precious 
metals from their ores. The process of extracting precious metal from the ore 
containing it, which consists in wetting the ore, in a pulverized condition, with 
just sufficient cyanogen-containing solution to moisten the ore and reduce the 
mass to the condition of mud, maintaining the saturated ore in a quiescent state 
for a prolonged period of time, then diluting the mass and subjecting it to agita- 
tion for a suitable period of time, separating the resultant solution from the ore 
by filtration, and finally precipitating the precious metal from said solution. 

578341 March 9, 1897. W. A. KONEMAN. Process of recovering precious- 
metals from cyanide solutions containing them. The process of recovering, by pre- 
cipitation, the precious metal or metals contained in a cyanogen-containing solu- 
tion, which consists in subjecting said solution to contact with an alloy composed 
of load and zinc, and in which lead is the preponderating metal in weight, or with 
an alloy composed of lead, zinc, and aluminv.m. 

580683 April 13, 1897. C. W. H. GCPNER and H. L. DIEHL. Recovery of 
gold and silver from their solutions. The process for the precipitation of gold and 
silver from their cyanide solutions, which consists in adding to Faid solutions a ^Jf 
Considerable quantity of cuprous cyanide, then adding an acid to effect precipi- 
tation, dissolving the latter by a fresh quantity of the cyanide solution obtained 
by leaching, and then adding acid to effect successive precipitations from said 

580948 April 20, 1897, J. C. MONTGOMERIE. Process of treating cyanide solu- 
tions. The process for the extraction of the precious metals from cyanide solu- 
tions, which consists in filtering the solution through a charcoal filter, heating 
the filtering material on the same becoming surcharged with cyanogen or its com- 
pounds, condensing the resultant gases and obtaining ammonium cyanide and ^Q/ 
other ammonium salts in solution, applying the regenerated charcoal (still con- 
taining the precious metals) in the filtration of a further charge or charges of the 
solution, and ultimately recovering from the charcoal the precious metals accu- 
mulated therein. 

587179 July 27, 1897. J H. BURFEIND. Treatment of gold and silver ores. As 
an improvement in the extracting of precious metals from their ores, the treat -^N^ 
ment of the cyanide product or precipitate containing said metals, preparatory 
to melting the said product with sulphurous acid. 

591753 October 12, 1897. E. J. FRASER. Process of obtaining precious metals 
by solution. The process of treating gold and silver ores by solution, which con- 
sists in converting the metal bases of dioxides of the alkaline metals into sulphates, 
by the addition of sulphuric acid, so as to produce hydrogen dioxide, preventing 
the decomposition of the hydrogen dioxide by an excess of acid, separating the 
solution from the metallic sulphate, mixing the solution with a solution of cj^anide 
of potassium and lime in the presence of a precious metal, and leaching the liquid 
holding the precious metal. 

592153 October 19, 1897. J. S. MACARTHUR. Precipitating precious metals 
from solutions. The process of precipitating a precious metal from a cyanide 
solution, which consists in subjecting said solution containing a base metal to 
the action of a precipitant protected by a metal inert in said solution. Such a 

378 . APPENDIX. 

precipitant is found in zinc, mercury, or copper protected by lead. When cop- 
per is present in the cyanide solution, this copper is removed by the precipitant 
prior to the removal of the precious metal. 

601201 March 22, 1898. S. NEWHOUSE, A. J. BETTLES, and T. WEIR. Method 
or process of extracting precious metals from their ores. A method or process for 
the extraction of the precious metals from their ores, said method or process con- 
sisting, first, in neutralizing the acidity of the ore where this condition exists; 
second, in placing the ore in a suitable solution of cyanide of potassium and sub- 
jecting the mass to agitation; third, in adding a quantity of zinc to the mixture 
of ore and cyanide and subjecting the mass to further agitation; and, fourth, in 
adding quicksilver or mercury charged with sodium amalgam, and finally agitating 
the entire mass for purposes of amalgamation. 

607719 July 19, 1898. M. E. WALDSTEIN. Process of recovering precious 
metals from their solutions. The process for extracting and recovering precious 
metals from their ores, which consists essentially of the following steps: First, 
subjecting the ore in a powdered state to the action of an aqueous solution of a 
cyanide; second, supplying to the solution charged with the precious metals that 
quantity of zinc dust determined to be exactly sufficient to precipitate said metals; 
third, agitating said solution and said zinc dust until said metals are precipitated 
and said zinc dust is absorbed; fourth, recovering the precious metals from the 
valuable precipitate of the preceding step by filtration, or other process. 

610616 September 13, 1898. H. L. SULMAN and F. L. TEED. Extraction 
of precious metals from their ores. The essence of this invention consists in the 
employment of haloid compounds of cyanogen in combination with free cyanide 
of potassium or other suitable cyanide of the alkalies or alkaline earths as a sol- 
vent for precious metals in their ores, examples of such haloid compounds of cyanogen 
being found in cyanogen chloride, or bromide or iodide. 

620100 February 28, 1899. W. A. CALDECOTT. Method of extracting gold 
from cyanide. An improved method for the precipitation of gold from gold-bear- 
ing cyanide solutions by passing such solutions over zinc shavings previously 
treated with a soluble salt of mercury, such as perchloride of mercury (HgCl 2 ). 

) May 2, 1899. C. B. JACOBS. Process of reducing metals from their 
solutions'. The process of reducing metals from their solutions, consisting in sub- 
jecting them to the action of gaseous phosphide of hydrogen in the presence of 
an alkaline material, thereby precipitating the noble metals in a metallic state 
and the base metals as phosphides, and then separating the latter from the noble 

625564 May 23, 1899, E. D. KENDALL. Process of treating gold or silver 
ores and composition of matter for same purpose. A composition of matter to be 
used for extracting precious metals from ores, tailings, or other bodies, consisting 
of a suitable thiocyanate and a suitable ferrocyanide in watery solution. 

625565 May 23, 1899. E. D. KENDALL. Process of treating gold or silver 
ores and composition of matter for same purpose. A composition of matter to be 
used for the extraction of precious metals from ores, tailings, or other bodies, con- 
sisting of a suitable thiocyanate and hydrogen dioxide in watery solution. 

629905 August 1, 1899. J. J. HOOD. Process of extracting gold or silver. The 
process of extracting gold, silver, and mercury from solutions by bringing the 
solutions into contact with an alloy of zinc, antimony, and mercury, from time 
to time distilling off mercury from the alloy, and finally recovering the gold and 
silver from it. The precipitant used consists of an alloy of about one hundred 
parts of zinc, five parts of antimony, and twenty parts of mercury. 

630982 August 15, 1899. W. KEMMIS-BETTY and B. SEARLE. Process of 
recovering gold from pulp, slimes, or similar substances. The process of extracting 
gold from ores, which consists of the following steps: First, dissolving the gold 
m the pulp in a weak solution of cyanide of potassium: second, adding a stronger 
solution of cyanide of potassium to the gold-bearing solution in the proportions 


specified; third, immediately after so strengthening the solution, passing the 
same through a body of zinc shavings coated with lead. 

635199 October 17, ,1899. J. SMITH. Process of treating gold or silver ores. The 
process for treating gold and silver ores, tailings, slimes, and like materials con- 
taining precious metals, which consists in mixing the material to be treated with 
caustic lime, saturating or covering the mixture entirely with water and keeping 
it thus until all the acid present has combined with the lime, drying the material, 
exposing it to the action of atmospheric air, and treating it with a cyanide. 

636114 October 81, 1899. J. S. CAIN, A. SODERLING, and S. M. MACKJNIGHT. 
Preliminary treatment of ores or tailings before cyaniding. The method or process 
of treating ores containing the precious metals, which conissts in first leaching 
said ores or tailings in a weak solution of nitric acid, or of nitric and sulphuric 
acids, subsequently leaching the same in an alkaline solution, and finally leaching 
the same in a cyanide solution. 

636288 November 7, 1899. H. DE RAASLOFF. Process of extracting precious 
metals from ores. The improvement in the process of separating precious metals 
from their ores, consisting in mixing with the ore a solution consisting of a base 
and a solvent for precious metals, which solvent is capable of being separated 
from the said base by oxygen, and adding liquid air to the ore and solution, or 
by evaporating the nitrogen from liquid air, and adding the oxygen which remains 
to the mixed ore and solution. 

? December 5, 1899. M. B. ZERENER. Precipitation of precious metals 
from their cyanide solutions. The process of precipitating gold and silver from 
cyanide solutions by causing the solution to move in one direction, and during 
such movement passing through it, in the opposite direction and in the form of 
a spray, or a number of fine streams or films, mercury charged with alkali metal. 

641818 January 23, 1900. C. WHITEHEAD. Process of extracting gold from 
ores. The process of extracting gold from ores in which the particles of free gold 
are enveloped in a compound of a base metal having the folio wing characteristics, 
to wit: non-siliceous, oxidized, practically impervious to a solvent solution, such 
as one of cyanide, not readily removable by washing with water, and insoluble 
in water, but soluble in dilute acids, consisting in first subjecting the crushed ore 
to the action of heat sufficient to convert the coating into a porous condition and 
afterwards treating the ore with a cyanide solution. 

642767 February 6, 1900. G. THURNAUER. Process of separating precious 
metals from their mixtures with zinc. The process of treating the mixture of zinc 
and precious metals resulting from the treatment of cyanide solutions of the precious 
metals by zinc, which consists in subjecting said mixture to the action of a solu- 
tion containing lead and then to the action t>f acid, whereby the zinc is dissolved 
and the precious metals remain in admixture with metallic lead. 

646006 March 27, 1900. J. C. MONTGOMERIE and H. PARKES. Treatment of 
gold and silver ores, etc. In the extraction of gold and silver from ores or compounds 
containing the same, the process consisting in treating the ore or compound with 
.a cyanide of an alkali metal, caustic alkali, and barium dioxide, in conjunction 
with ammonium sulphate. 

646808 April 3, 1900. T. CRUSE. Method of extracting gold and silver from 
iheir ores. The process of recovering precious metals from their ores, which con- 
sists in first heating the ore pulp to the boiling-point, adding cyanide of potassium 
to the hot mass, permitting the mass to gradually cool, and while it is cooling add- 
ing to the mass the following: Eluestone, iron sulphate, sulphuric acid, and quick- 

649628 May 15, 1900. W. A. CALDECOTT. Extraction of gold or other precious 
metals from slimes. The method of extracting precious metals from finely divided 
materials, such as slimes, containing reducing substances, such as ferrous sulphide 
or hydrate, which consists in rendering the material alkaline, then forcing air 
into the pulp until the ferrous compounds are converted into ferric hydrate, then 
adding cyanide and continuing aeration and agitation until the precious metals 
are dissolved. 


651509 June 12, 1900. F. W, MARTINO and F. STUBBS. Precipitation of 
precious metals from cyanide solutions. A process for the precipitation of the 
precious metals from their aqueous cyanide solutions, consisting in passing acetylene 
and atmospheric air through such solutions, or by adding calcium carbide to them, 
and precipitating the metals in a metallic state. 

651510 June 12, 1900. F. W. MARTINO and F. STUBBS Treatment of ores 
and precipitation of precious metals ffom their cyanide solutions. A process for 
the precipitation of precious metals from their aqueous-cyanide solutions, con- 
sisting in treating such solutions with a hydrocarbon gas, produced when a metallic 
carbide is decomposed by water, and capable of precipitating the metals in a metallic 
state. Aluminum carbide is given as an example of such a metallic carbide. The 
use of methane as a precipitant is also claimed. 

657181 September 4> 1900. H. DE RAASLOFF. Process of separating precious 
metals from their ores. The continuous process of treating ores of precious metals, 
consisting in mixing the finely divided ore with a suitable solvent for the precious 
metals, inducing the mixture to flow continuously from and back to the point 
of admixture, while so flowing introducing liquid oxygen or liquefied air into the 
mixture, then causing the mixture to flow with sudden variations of velocity to 
agitate it, then separating the solution from the base earthy mineral matter, and 
sending it continuously through an electrodepositing ,bath, where the precious 
metal is deposited, and thus in continuous ordered succession. 

656395August 21, 1900. E. H. DICKIE. Process of leaching ores or tailings. 
The improvement in the process of leaching ores or tailings with a solution which 
dissolves the precious metals, which consists in adding to the solution an agent 
composed of an acetate of an alkali metal or of alkali-earth metals which is capable 
of readily uniting with and forming acetates of the base metals, and which has 
little or no affinity for the precious metals, thereby enabling the solvent to act 
directly upon the latter, and then leaching the ores. Calcium acetate is cited 
as an example of an acetate of an alkali-earth metal. 

664080 December 18, 1900. J. P. SCHUCH, Jr. Process of extracting precious- 
metals from their ores. A method of extracting precious metals from their ores, 
which consists in combining the crushed ore with a cyanide solution while both 
are in a warm condition, mechanically mixing the ore and solution by agitation 
simultaneously with the commingling thereof, charging the mixture during the 
agitation with hot air, and finally separating the ore and slush or pulp from the 
metal in solution. 

665105 January 1, 1901. J. C. KESSLER. Process of extracting gold and 
silver from ores. The process of separating precious metals from auriferous and 
argentiferous ores, consisting, first, in subjecting the ores to the action of an aque- 
ous solution, consisting of cyanide of alkali metal, yellow prussiate of potassium, 
and permanganate of an alkali metal in substantially the proportions of water, 
one thousand (1000) parts; yellow prussiate of potassium, two and one-half (2.5) 
parts; cyanide of alkali, two and one-half (2.5) parts; parmanganate of potas- 
sium, one-tenth (0.1) part, until the gold and silver contained in such ores are 
dissolved; second, separating the metals from their solution by the application 
of a soluble lead salt, by which the cyanide solution is decomposed and a non- 
soluble cyanide of lead is formed, at the same time a non -soluble cyanide of gold 
or silver is precipitated; third, by the application, to the sediment thus precipi- 
tated, of sodium amalgam, whereby a gold, silver, and lead amalgam is produced 
and at the same time a concentrated solution of cyanide and ferrocyanide of sodium 
is regenerated; and, fourth, diluting the concentrated cyanide solution with a 
quantity of water and regenerating and reenergizing the aqueous solution for 
reuse by the addition of permanganate of alkali. 

671704 April 9, 1901. E. D. KENDALL. Process of treating ores containing 1 
silver or silver and gold. The process of treating ores or other bodies for the extrac- 
tion of precious metals, which consists in treating them with a suitable chemical 
solution containing a thiocyanate and a cyanide, capable of dissolving silver and 
gold, and in then treating the so-dissolved silver by a suitable sulphide, such as 
potassium sulphide, and in so regulating; the amount of the sulphide to the silver 


as that they shall substantially equalize each other in separating the sulphur sul- 
phide and in returning the thiocyanate and cyanide into subsequent operations 
for further treatment of the ore. 

673425 May 7, 1901. G. A. DUNCAN and F. H. BEACH. Method of treating 
precious metal-bearing ores. The method of treatment of precious metal-bearing 
ores to cause the precious metal to be dissolved from the ore, and the resulting 
metal-bearing liquor and impoverished ore to be separated from each other, which 
consists in the following steps: First, maintaining a substantially continuous 
supply stream of mingled comminuted ore and solvent liquor; second, mechani- 
cally dispersing such mingled ore and liquor into the air, in a direction transverse 
to the onward movement of the stream, without separating the ore from the liquor; 
third, delivering the resultant stream of mingled metal-bearing liquor and impov- 
erished ore and receiving the same in mingled condition and carrying it onward; 
fourth, sucking the liquor from the tailings; fifth, delivering water to the impov- 
erished tailings remaining, and subsequently sucking such wash-water therefrom;, 
sixth, delivering such impoverished ore or tailings after the application cf such 

682612 September 17, 1901. E. L. GODBE. Method of leaching ores. The- 
method of leaching ores, which consists in disposing moistened ore in superim- 
posed strata within a containing receptacle by a continuous mechanical agitation 
in the lower portion of the latter to form a lower thoroughly agitated stratum of 
heavier portions of the ore, a stratum of lighter portions or particles next above 
which are agitated to a less degree, a stratum of slimes and other lighter particles 
next above which remain substantially immobile, and a top covering of a clear 
supernatant solution, introducing the ore below the upper surface of said latter 
solution, overflowing and carrying off the clear solution, replacing water in the 
charge by a cyanide of potassium solution introduced at the bottom of the recep- 
tacle below the lower heavier stratum and causing it to percolate upwardly through 
the strata above, increasing the agitation during the introduction of said cyanide 
solution, carrying off the metal-bearing cyanide solution which overflows from the 
top of the charge and precipitating the said overflow metal-bearing solution after 
it leaves the receptacle. 

689190December 17, 1901. B. HUNT. Process of precipitating and recover- 
ing precious metals from their solutions. -The process of precipitating precious 
metajs, consisting of adding to the pulp a cyanide solution and agitating the same 
until the metal is extracted; then adding to the pulp, while continuing the agita- 
tion thereof, powdered metallic aluminum whereby the precious metal is precipi- 
tated, but in suspension in the pulp; then adding mercury and continuing the 
agitation until the metal is in the form of an amalgam, and finally recovering 
the precious metal by treating the amalgam. 

692634- February 4> 1902. H. DAVIS. Process of extracting precious metals 
from their ores. A process for the extraction of the precious and other metals 
from ore, ore pulp, sands, slimes, tailings, mineral-bearing earths or other sub- 
stances containing these metals, which consists in introducing chlorine gas into 
the ore and afterwards wholly or partially removing the excess of chlorine by 
forcing air into the material and afterwards treating with a cyanide solution to- 
dissolve the chlorides. 

f March 4, 1902. B. W. BEGEER. Cyanide process of extracting pre- 
cious metals from ores. The process of treating material containing the precious 
metals, consisting in setting in motion in an endless path a solution of cyanide 
of potassium, introducing oxygen to the moving liquid, and finally subjecting 
the metal-bearing material to the action of said solution. 

March 25, 1902. E. SCHILZ. Cyanide process of extracting precious 
metals from their ores. An improved process in the art of extracting precious v v 
metals from their ores, said process consisting in thoroughly and intimately mix- 
ing peroxide of barium (BaO 2 ) with precious metal-bearing rraterial, and then 
subjecting the same to treatment with an alkaline-cyanide solution. 

701002 May 27, 1902. J. B. DE ALZUGARAY. Method of extracting precious 
metals from their ores. The process for treating ores containing precious metal 


and consisting in adding the crushed ore to a solution of sodium chloride, sodium 
carbonate, and potassium cyanide, then forcing through the mass a gaseous mix- 
ture of bromine and air and recovering the precious metals from the solution by 
any known means, such as electrolysis. 

702305 June 10, 1902. E. D. KENDALL. Process of extracting precious 
metals from their ores. The process of treating ores carrying precious metals, 
which consists in treating such ore with a lixiviating solution, consisting of a cyanide, 
potassium percarbonate, and water, and finally extracting the precious metal from 
such lixivium. 

705698 July 29, 1902. R. H. OFFICER, J. W. NEIL, J. H. BURFEIND, and 
F. H. OFFICER. Cyanide . process of working gold, silver, or other ores. The im- 
provement in treating ores by the cyanide process, consisting in agitating the 
pulp containing the cyanide solution by a suitable gas under pressure, passing 
the gas and the hydrocyanic-acid gas liberated from the solution through a regen- 
erating solution, and using the gas after passing through said regenerating solu- 
tion to agitate a fresh quantity of pulp. 

708303 August 5, 1902. L. B. DARLING. Process of extracting precious 
metals from ores. The process of extracting precious metals from finely divided 
materials or ores, which consists in spreading a comparatively thin layer of the 
material over a substantially flat and large working surface provided with drain- 
age ducts or channels; then covering said material with suitable metal-dissolving 
or cyanide solution; then passing a heavy roll back and forth over the charge 
of material, etc., thereby at the same time thoroughly agitating or stirring the 
charge and forcing some of the solution into the drainage ducts; then discharg- 
ing said solution into the sump, and finally precipitating the precious metal from 
the solution. 

707926 August 26, 1902. W. HILT and C. E. LANE. Process of extracting 
precious metals. The 1 process of extracting precious metals from solutions thereof, 
which consists in producing cyanide solutions of said metals, vaporizing metallic 
^inc by means of heat, and conducting the vapor thus formed to a point beneath 
the surfaces of said solutions, thus producing finely divided zinc, which replaces 
the precious metals and thereby causes their precipitation. 

708504 September 2, 1902. H. L. SULMAN and H. F. KIRKPATRICK-PICARD. 
Treatment of ore slimes. The process of treating ore slimes, which consists in sepa- 
rating, by means of a centrifugal machine, the ore slimes from the residual water 
with which they are mixed by adding a little lime to the charge, removing the 
bulk of the water, thereafter introducing into the machine an amount of 
leaching solution of a volume equal to that of the remaining quantity of adhering 
moisture and introduced into the slimes by centrifugal action, and replacing ]the 
moisture by the added leaching solution. 

710496 October 7, 1902. S. T. MUFFLY. Process of treating ores. The process 
of treating ores, which consists in injecting into said ores, as they are agitated 
and elevated and allowed to fall by gravity in a closed chamber, a chemical solu- 
tion in the form of a spray, together with hot air under pressure, and allowing 
the elements and fumes freed by this operation to escape from said chamber. 

718633 January 20, 1903. T. B. JOSEPH. Gold-extracting process. The 
process of extracting gold or silver from ore containing the same, when in a suit- 
able condition, which consists in subjecting the said ore to the leaching action of 
a solution of water, cyanide of potassium, hydrate of calcium, and carbonic-acid 
gas, and introducing an oxidizing agent into the solution, and subsequently pre- 
cipitating the gold from this solution. 

719274 January 27, 1903. Z. B. STUART. Process of extracting metals from 
ores. The process of extracting precious metals from ores, consisting in agitating 
the pulp together with cyanide, water, and air by ebullition in one vessel, 
causing the mixture to assume an even consistency throughout, and passing the 
mixture through a mechanical agitator and combining therein a relatively smaller 
quantity of mixture with a relatively larger quantity of air and there forcing the 


pulp, cyanide, water, and air into intimate contact, and circulating the mixture 
through the two vessels. 

722455 March 10, 1903. AUGUST PRISTER Process of precipitating gold 
from cyanide solutions. The process for the precipitation of gold or other precious 
metals from cyanide solutions, such as potassium cyanide, sodium cyanide, and V/ 
bromine cyanide, which consists in acidifying the solution, adding a solution con- 
taining salts of mercury and copper, and then adding a solution containing zinc 
salts and a small percentage of a potassium ferrocyanide, or a small quantity of 
the cyanide solution discharged from the ordinary zinc-precipitation Boxes. 

? March 17, 1903. J. P. SCHUCH, Jr. Process of separating precious 
metals from solvent solutions. The process of separating precious metals from 
their solvent solutions, which consists, first, in passing the solution through 
crushed limestone or phonolite to neutralize any free acid, then through zinc, 
wood ashes, asbestos wool or its equivalent, and charcoal or coke, to neutralize 
any free soda or carbonates, then through zinc shavings to precipitate the pre- 
cious metals, then through charcoal to filter the solution and effect retention of 
a percentage of the precious metals, then through limestone or crushed phono- 
lite to effect precipitation of zinc contained in the solution, and then alternately 
through zinc, charcoal, or coke and zinc to effect complete separation of the pre- 
cious metals and thorough filtration of the solution. 

725895 April 21, 1903. M. V. USLAR and G. ERLWEIN. Process of extract- 
ing gold. The process for extracting gold from auriferous ores, which consists in x\ 
lixiviating the ores with a solution of potassium cyanide, rhodanides, hyposul- 
phites, and sodium chloride. 

726294 April 28, 1903, F. J. HOYT. Method of extracting gold from ores. 
The method of milling gold ore, consisting of the following steps: First, pulverizing 
the ore; second, distributing the ore thinly over a wide, long, and open sluice- 
way; third, flowing the ore and propelling it forward over its bed by the action of 
a stream of chemical solution adapted to dissolve the ore; fourth, automatically 
screening and separating the solution from the tailings by the same force; and 
fifth, subjecting the solution to a reagent to precipitate the gold therein. 

727659 May 12, 1903. F. W. MARTINO. Method of extracting noble metals. 
The process of recovering gold from its cyanide solution, consisting in acidify- ,, 
ing the solution and treating it at a raised temperature with barium sulphocar- "; 
bide. The latter is manufactured by fusing two parts, by weight, of barium sul- 
phate (baryta or heavy spar) BaSO 4 in an electric furnace with one part of carbon. 

728397 May 19, 1903. T: B. JOSEPH. Gold-extracting process. The process 
of extracting gold and silver from ore containing the same when in a suitable con- 
dition, which consists in subjecting the said ore to the leaching action of a solu- 
tion of water, cyanide of potassium, hydrate of calcium, peroxide of barium and 
carbonic-acid gas, the ore being agitated by compressed air. 

730835 June 9, 1903. D. MOSHER. Ammonia cyanide process of treating 
copper, nickel, or zinc ores containing precious metals. The process of treating 
refractory sulphur, tellurium, and arsenical ores containing copper, zinc, nickel, 
gold, and silver, consisting in first roasting such ores at a low red heat to trans- 
form the metals so transformable into sulphates, arsenates, or tellurates; then -N/V 1 
oxidizing reducing compounds by very dilute ammonia; and subsequently extract- ' 
ing the metals with an ammoniacal-cyanide solution containing an excess of cupric 
oxide or hydroxide over and above that necessary to form metallic cyanide double 

731169 June 16, 1903. O. A. ELLIS. Apparatus for extracting metals from 
ores. An apparatus for extracting metals from ores, having in combination 
a receiving hopper having an inclined bottom, a discharge opening in said hopper, 
an inclined chute leading from said hopper and provided with a screen, a pre- 
cipitating box connected with said inclined chute, means for causing a flow of 
chemical solution through said hopper, chute, and precipitating box, and means 
for passing a current of electricity through said precipitating box. 


731631 June 23, 1903. J. T. TERRY, Jr. Extracting gold or silver from, 
slimes. An improvement in separating precious metals from slimes with which 
they are mixed, consisting in forming a solution with water, spraying said solu- 
tion into tanks containing a cyanide solution made dense by the addition of salt, 
allowing the slime to settle through and into the solution, then drawing the clear 
liquor from the top through vertically disposed filters and discharging the sludge 
from the bottom into succeeding tanks containing a similar cyanide solution, 
allowing it to settle and again drawing off the clear liquor. 

731839 -June 23, 1903. G. A. BAHN. Sulphuric acid process of extracting- 
precious metals from solutions. The process of . precipitating precious m3tals from 
solutions thereof, which consists in producing cyanide solutions of said precious 
metals, then acidulating with sulphuric acid said cyanide solutions, then immers- 
ing zinc in sheet, plate, or other form in the acidulated-cyanide solution contain- 
ing the precious metals; the chemical action thereupon taking place in the solu- 
tion, dissolving zinc and precipitating the precious metals; then recovering from 
the precipitate of the preceding operation the precious metals by filtering and 
melting, or other process. 

732605 June 30, 1903. G. E. THEDE. Process of leaching ores. The proc- 
ess of leaching ores which consists in mixing with the ore to be treated a cyanide 
solution, peroxide of hydrogen, and an oxide which is reducible by said peroxide of 

732639 June SO, 1903. T. B. JOSEPH. Gold-extracting process. The process 
of extracting gold and silver from ore containing the same, when in a suitable 
condition, which consists in subjecting said ore to the leaching action of a solution 
containing water, cyanide of potassium, bromine, hydrate of calcium, peroxide 
of barium, and carbon dioxide, said carbon dioxide being forced into the leaching 
solution simultaneously with compressed air. 

738758 September 15, 1903. J. B. DE ALZUGARAY. Extraction of precious 
metals from their ores. The process for extracting precious metals from their 
ores, consisting in first moistening the crushed ore with an alkaline solution and 
afterwards agitating it in a solvent solution and blowing through it an oxidizing 
agent composed of gaseous bromine, and its acid and oxyacid compounds dissolved 
in air, and finally recovering the metals from the solvent in any well-known manner 

745490 December 1, 1903. T. J. GRIER. Process of extracting precious metals. 
The process of extracting precious metals from slimes, consisting in directing the 
slimes into a settling-tank, drawing off the thicker portions of the slimes and 
depositing the same into a leaching-vat, of introducing a cyanide solution under 
pressure through perforations in* the false bottom of the vat, causing the watery 
portions of the slimes to be displaced by said cyanide solution, then treating the 
charge with an air under pressure, and afterwards introducing through the false 
bottom of a vat a salt solution of greater density than the cyanide solution to 
displace the latter. 

745828 December 1, 1903. E. B. HACK. Process of extracting metals from 
ores. A cyanide process, consisting of the following steps in the order named: 
Caking the pulp by pressure under conditions allowing the moisture to escape; 
introducing a weak solution of the solvent simultaneously with the introduction 
of air under pressure; drying the pulp by passing air under pressure therethrough; 
introducing a stronger solution of the solvent simultaneously with the introduc- 
tion of air under pressure; and finally drying the cake by air pressure. 

755951 March 29, 1904- J. SMITH. Process of treating ores. In the cyanide 
treatment of ores, the method of rendering insoluble in the cyanide solution ferrous 
oxide contained in a mass of moist crushed ore, which method consists in apply- 
ing heat to said mass in the presence of air, previous to >its treatment by the 
cyanide solution. 



Subclass 15 Aqueous Bath, Ores. 

61866 February 5, 1867. J. H. RAE. Improved mode of treating auriferous 
and argentiferous ores. This invention consists in treating auriferous and argen- 
tiferous ores with a current of electricity or galvanism for the purpose of separat- 
ing the precious metals from the gangue. In connection with the electric current 
suitable liquids or chemical preparations, such, for instance, as cyanide of potas- 
sium, are used, in such a manner that by the combined action of the electricity 
and of the chemicals, the metal contained in the ore is first reduced to a state of 
solution and afterwards collected and deposited in a pure state. Among the 
claims is one for the use of the platinum agitator as an electrode. 

Q2776 March 12, 1867. J. H. RAE. Improved mode of collecting gold and 
silver from sweepings, washings, etc. This invention consists in treating sweepings, 
filings, and washings containing gold or silver with a current of electricity or gal- 
vanism for the purpose of separating the precious metals from the impurities of 
foreign matter mixed with them. In connection with the electric current suitable 
liquids or chemical preparations, such, for instance, as cyanide of potassium, 
are used in such a manner that by the combined action of the electricity and chemi- 
cals the precious metals contained in the sweepings, filings, and washings are 
first reduced to a state of solution, and afterwards collected and deposited either 
as oxides or in a metallic state, and the operation of extracting or separating said 
precious metals from the sweepings, filings, or washings is attended with very 
little trouble and expense. During this operation the bath which contains the 
washings, filings, or sweepings acts as an electrode, and also as an agitator; and 
the third claim of the patent covers the use of this carbon electrode as an agitator. 

90565 May 25, 1869. W. J. LYND. Improved process of separating iron 
and other metals from potters' clay. The process of removing iron, copper, and 
other discoloring matters from potters' clay and other argillaceous substances by 
subjecting the clay, when in solution, to the action of one or more magnets, or 
by passing through the bath containing such solution a current of electricity. 

239300 March 22, 1881. A. RYDER. Apparatus for treating ores. The 
invention has reference to apparatus for reducing ores in which the ore, while in 
a heated state, is dumped suddenly into a liquid or chemical solution for the pur- 
pose of disintegrating the ore and separating the particles preparatory to amal- 
gamation. And the inventor claims, in an apparatus for disintegrating ores pre- 
paratory to amalgamation, the insulated vessel or non-conductor of electricity, 
provided with a metallic or plated hopper, in combination with an electrical gen- 
erator or battery and conducting wire or wires. 

246201 August 23, 1881. E. REYNIER. Electrochemical treatment of ores. 
The method of treating ores of zinc and lead for the production of electricity and 
recovery of the metals by acting upon said ores in a voltaic couple with an elec- 
trolytic liquid haying caustic alkali as the base, and precipitating the metallic 
oxides from said liquid. 

272391 February 13, 1883. A. THIOLLIER. Process of and apparatus for 
extracting metals from their ores. In combination with an electrogenerator, a recep- 
tacle for conductively prepared ore or other material containing metal to be recov- / 
ered, having attachments for the negative and positive polar conductors of the x ^ 
electrogenerator, arranged, as described, in electrical communication with the / 
mass of conductive ore by means of the electrolytic solution, whereby reduction 
is effected when the current is passed. 

286208 October 9, 1883. L. LETRANGE. Process of and apparatus for reducing 
zinc ores. The process of reducing zinc ores and producing pure metallic zinc 
and sulphuric acid simultaneously therefrom, which consists in simultaneously 
roasting sulphuret ores and carbonate ores in the fame or communicating chambers, 
and thereby converting both ores into soluble sulnhates, then leaching these roasted 
ores, and then depositing the metallic zinc from a solution of the sulphates by 


electric currents on metallic plates, and drawing sulphuric acid at the same time 
from the solution as fast as set free by the said electric currents; and the appa- 
ratus for use in the process of reducing zinc ores, which consists, essentially, in a 
reservoir for the sulphate solution; a precipitating vessel provided with suitable 
anodes and cathodes; a pipe provided with a regulating cock, leading from the 
reservoir to near the bottom of the precipitating vessel, and an outlet pipe for 
the freed acid, arranged in the said vessel at the desired level of the liquid therein, 
whereby the strength and quantity of the sulphate solution in the precipitating 
vessel are maintained constant. 

291670 January 8, 1884. M. BODY. Process of and apparatus for obtain- 
ing gold and silver from their ores by combined electrolytic and amalgamating proc- 
esses. The method of first subjecting gold and silver ores to the action of ferric 
salts, in combination with the electrolytic process, and the subsequent amalga- 
mation of the metals with mercury under the continued action of the electric cur- 
rent: and the apparatus for effecting this process. 

300950 June 24, 188 '4. H. R. CASSEL. Process of and apparatus for the 
separation of metals from ores and alloys. The process of separating metals from 
ores or alloys, especially those of an auriferous character, which consists in charg- 
ing the ore or alloy in a powdered condition into an anode compartment, which 
is separated from the cathode compartment by porous material, said anode com- 
partment containing a solution yielding nascent chlorine under the action of an 
electric current, and agitating said powdered material within said solution during 
the passage of the electric current; and the combination in an apparatus for treat- 
ing ores and metals by electrolysis, of a cathode compartment, a negative pole 
therein, a rotary drum constituting the anode compartment, provided with por- 
ous material separating it from the cathode compartment, and with a series of 
carbon rods or plates arranged within the same, and suitable electric connections. 

800951 June 24, 1884. H. R. CASSEL. Process of chloridizing ores by elec- 
trolysis In the process of extracting gold from rebellious or refractory gold ores, 
the steps which consist in subjecting the ore to the action of a solution yielding 
nascent chlorine under electrolytic decomposition, and adding lime or its equiv- 
alent, whereby acids formed by secondary action during said decomposition are 

317245 May 5, 1885. E. P. THOMPSON. Apparatus for the separation of 
gold from its ores by electrochlorination and deposition. The combination, with 
an electrolytic cell for separating chlorine from its compounds and its anode, of 
a battery, a cathode consisting of a pipe through which steam is admitted to 
the cell for the purpose of increasing the rapidity of the separating, and conduc- 
tors respectively connecting the same anode and cathode with the poles of said 

317246 May 5, 1885. E. P. THOMPSON. Apparatus for the electrodeposition 
of gold from its chlorides. The combination, in an electrolytic cell, of an anode 
formed of a series of carbon rods set in a metal ring, and a cathode formed by two 
thin corrugated copper plates connected electrically, which are set, respectively, 
within and without the circle of carbons. 

332705 December 22, 1885, H. H. EAMES. Apparatus for chloridizing gold t 
silver, and other ores. This invention consists of an iron vessel cylindrical in shape, 
lined with wood, having a cast-iron cover, adjusted so as to be steam- and vapor- 
tight. It is also arranged with a set of stirrers, to which motion is communicated 
by crown- and pinion- wheels. It is also fitted with pipes, by means of which steam 
can be forced through the contents and held there under pressure. It is also 
furnished with two electrodes, by which electricity can be passed through the 
ore and chemicals operated upon, while the pressure is applied. The electric 
current is best obtained from a dynamo machine of ordinary construction used 
in the deposition of metals. 

333815 January 5, 1886. M. BODY. Process of obtaining gold, silver, copper, 
nickel, and cobalt from their ores by electrolytic action. The process of separating 
gold, silver, copper, and other metals from chlorinated or chlorine-containing 
ores by electrolytic action, consisting in first roasting the ores or subjecting them 


to an equivalent oxidizing treatment, as specified, and then subjecting the ore 
to the action of ferric-salt solutions, and at the same time passing an electric cur- 
rent through said solution, whereby the metal becomes dissolved and precipitated, 
and chlorine gas is generated at the positive pole, which reconverts the resulting 
ferrous salts into ferric salts. 

351576 October 26, 1886. H. R. CASSEL. Process of extracting gold, etc.,, 
from ores. The process of separating metals from ores or alloys, especially those 
of an auriferous character, which consists in charging the ore or alloy in a pow- 
dered condition, into an anode compartment, which is separated from the cathode 
compartment by a porous partition composed of asbestos, which permits the pas- 
sage of the current with the metals in solution, and retains the ores within the 
anode compartment, said anode compartment containing a chloride solution, 
agitating and subjecting the charge to nascent chlorine produced from said 
solution during the passage of the electric current, passing the solution of metals 
through the asbestos partition, and depositing the metals in solution at the 

357659 February 15, 1887. D. G. FITZGERALD. Obtaining chlorine by electroly- 
sis. The electrochemical generation of chlorine by means of an anode of per- 
oxide of lead in the form of dense, highly conductive layers, plates, or masses of 
any required form preferably obtained by the means hereinbefore described, the 
said anode being employed in conjunction with any suitable cathode and with 
an electrolyte capable of evolving chlorine. 

360852 April 12, 1887. H. R. CASSEL. Apparatus for separating metals 
from ores or alloys. In an apparatus for separating metals from ores or alloys 
by electrolysis the combination of a journaled drum provided with carbon anodes, 
a hollow metallic shaft insulated on its exterior and extending through said drum, 
said shaft being perforated within the drum and separated from the interior there- 
of by a filter, and a screw conveyor within said hollow shaft. 

360853 April 12, 1887. H. R. CASSEL. Apparatus for separating meals 
from ores or alloys. In an apparatus for separating metals from ores or alloys by 
electrolysis the combination of a rotary drum constituting the anode compart- 
ment and having a suitable electric connection, a rotary cathode compartment 
having a suitable electric connection and provided with an automatic valve, a 
porous diaphragm separating said anode and cathode compartments, a fixed 
bracket, and an arch-shaped arm attached to said bracket in the path of said valve 
for opening of the latter. 

362022 April 26, 1887. H. LIEPMANN. Apparatus for separating metals from 
ores or alloys by electrolysis. In an apparatus for separating metals from ores 
or alloys by electrolysis the combination of an anode compartment, a cathode 
compartment, a filtering diaphragm separating said compartments, a dense por- 
ous diaphragm for separating said compartments during one step of the operation, 
and mechanism whereby the dense porous diaphragm may be placed in opposition 
with or removed from the opening between the anode and cathode compartments. 

379764 March 20, 1888. C. F. CROSELMIRE. Wet process of extracting pure 
zinc from its ores. The process which consists in immersing roasted zinc ore in 
dilute acid, passing an air blast through the solution until the impurities are oxi- 
dized, and finally drawing off the zinc solution and depositing or precipitating the 

387036 July 31, 1888. C. P. BELLOWS. Process of cleansing gold and silver 
where mechanically coated in ores with refractory substances. The process of cleans- 
ing refractory ores prior to the recovery of the precious metals therefrom, which 
consists in immersing said ores in a solution of a sodium chloride and caustic 
soda, heating said solution, and at the same time subjecting the ores to the action 
of the electric current, whereby the ore is rendered free milling. 

391360 October 16, 1888. H. H. EAMES. Apparatus for chloridizinq ores. 
In a device for chloridizing metallic ores, the combination of a hermetically sealed 
tank, metallic plates placed inside the said tank and mounted upon insulated sup- 
ports, whereby they will be insulated from each other and from the tank, the said 
plates forming the two elements of a galvanic battery, a stirrer placed in the said 


tank and between the said plates a solution containing the ore to be treated, by 
which a galvanic current will be excited between the said charging steam in the 
said tank, whereby the said solution will be heated and a pressure maintained in 
said tank. 

399209 March 5, 1889. J. H. RAE. Electric amalgamator. In an apparatus 
for working ores, a pan or tub with an internal copper ring and rotating arms or 
stirrers, in combination with a horizontal wooden ring suspended above the tub, 
a copper plate forming the upper surface of said ring and perforated to admit car- 
bons which pass loosely through the plates, said carbons having heads or trans- 
verse pins at the upper ends, and the movable elastic plates or springs pressing 
upon the heads of the carbons to hold them in contact with the copper plate. 

407386 July 23, 1889. J C. WISWELL. Bath or solution for separating metals 
from their ores. The process of producing a bath or solution for the separation of 
metals from their ores, consisting in subjecting a solution of salt water, muriate of 
ammonia, and muriatic acid to a current of electricity, then placing this solution 
in a tank containing liquid mercury, and subjecting the whole to a current of elec- 
tricity, said mercury serving as the anode. 

410228 September 3, 1889. J. C. WISWELL. Solution for use in separating 
metals from their ores. A solution or bath for use in separating metals from their 
ores, consisting of chlorine in solution, sodium chloride, ammonium chloride, 
hydrochloric acid, and bichloride of mercury. 

415576 November 19, 1889. W. VON SIEMENS. Process of electrodeposition 
of metals. The process which consists in lixiviating ore in separate vessels with a 
solution containing ferric sulphate, passing the resulting ferrous sulphate succes- 
sively through a series of compartments containing cathode plates, and in which 
cells the solution is subjected to the action of an electrical current by which the 
metal in solution is deposited, then passing the remaining liquid successively 
through a second series of compartments containing anode plates of insoluble 
material and separated from the first-mentioned compartments by non-metallic 
diaphragms, whereby the ferrous sulphate is oxidized and reconverted into ferric 
sulphate, which solution is again used to lixiviate ores. 

418134 December 24, 1889. H. F. JULIAN. Process of extracting gold and 
silver from their ores. The improvement in the process of extracting gold and 
silver from ores, which consists in agitating the pulverized ore in closed vats with 
chlorine, bromine, or iodine and water under pressure of a fluid forced into the vat, 
and aftef the gold and silver have combined with the halogen, adding mercury 
and again agitating under pressure of a fluid forced into the vat, next passing the 
ore, mercury, and solution over amalgamated copper surfaces forming the cathode 
of an electric circuit, and subsequently submitting the mixture to electrolytic 
action between cathodes of mercury below and suitable anodes above. 

452125 May 12, 1891. W. VON SIEMENS. Apparatus' for extracting metals 
from their ores. The combination of a trough for the flow of liquid, composed 
of numerous sections connected at alternate ends, with an inlet at one end and 
an outlet at the other, with two longitudinal shafts in each section of the said 
trough, said shaft carrying beaters and being entirely immersed in the liquid 
contained in the trough, and a heating pipe located below and between the said 

459023 September 8, 1891. C. SCHREIBER and H. KNUTSEN. Process of 
extracting antimony from ores. In the extraction of antimony from ore, the proc- 
ess which consists in subjecting the crushed ore to the action of a solution of sulphide 
of sodium and then precipitating the antimony in metallic form by electrolysis, 
adding hydroxide of sodium to the solution. 

460354 September 29, 1891. W. VON SIEMENS. Apparatus for eUctrolytically 
separating metals from ores. In an electrolytical cell, the combination of a revolv- 
ing cathode, a trough-shaped anode situated below the said cathode, in the trough 
of which the cathode revolves, a screen permitting the passage of the electrolyte 
and of electricity and capable of preventing the passage of vibrations of the elec- 
trolyte situated between the said cathode and anode, and means for supplying 
the electrolyte above the screen and for withdrawing the oxidized liquid from 
the bottom of the trough of the anode. 



473105 April 19, 1892. G. J. ATKINS. Electrolytic apparatus for separating 
gold and other metals from their ores. Electrolytic apparatus for separating gold 
and other metals from their ores, which consists of an upright anode compartment 
through which the ore is passed continuously, having within it an anode constructed 
to receive and retard the descent of the ore, while the ore itself forms a, more or 
less soluble portion of such anode pole, and an upright cathode compartment and 
pole, the said anode and cathode compartments communicating through an open- 
ing closed by a porous diaphragm and having outlets at their lower ends for the 
removal of the ore which has been acted upon in the anode compartment and of 
the metals and other substances that have been deposited or precipitated in the 
cathode compartment. 

484869 October 25, 1892. G. J. ATKINS. Process of separating gold and 
other metals from their ores. The continuous process of separating gold and other 
metals from their ores, which consists in passing such ore through the anode com- 
partment of an electrolytic apparatus in contact with the anode and retarding 
the descent of the ore in the said anode compartment while such ore is kept in con- 
tact with the anode pole of such compartment, so as to form a more or less soluble 
portion of such anode pole, and then subjecting the ore to the process of amalga- 

495212 April 11, 1893. J. F. WISWELL. Process of and apparatus for 
treating ores. An improved process of treating ores which consists in submerging 
mercury in a solution of common salt connecting the mercury with the positive 
pole of a generator and the salt solution with the other pole, so that the current 
will decompose the salt solution and cause the chlorine to be attracted to the mer- 
cury forming calomel; ^ treating the calomel with aqua regia forming a soluble 
mercuric chloride, diluting the latter with water, treating undecomposed salt solu- 
tion with an electric current to produce sodium hypochlorite and introducing 
the soluble mercuric chloride and sodium hypochlorite simultaneously upon the 
crushed ore. 

495637 April 18, 1893. J. PFLEGER. Process of extracting zinc by electrolysis. 
The process of obtaining zinc by electrolysis out of a zinc-containing anode, 
which consists in adding to the bath a basic zinc-salt solution adapted to act as 
electrolyte, to which basic zinc-salt solution a conducting neutral salt has been 

495715 April 18, 1893. S. R. WHITALL. Process of lixiviating ores. The 
process of separating gold and silver from their ores, which consists, first, in roast- 
ing the ore to oxidize the base metals; and, secondly, in subjecting the roasted ore 
to the action of a solution of potassium cyanide and sodium hyposulphite, and 
subsequently precipitating the dissolved metals; and the process of separating 
gold and silver from siliceous ores, which consists in subjecting the ore admixed 
with caustic soda and potash to the action of a solution of potassium cyanide and 
sodium hyposulphite. 

497014 May 9, 1893. F. W. CLEGHORN. Process of separating precious 
metals from ores. The process of separating gold and silver from ores, consisting 
in filtering through the ores a solution of sulphuric acid and salt, and precipitating 
the gold and silver in the filtrate solution by placing metallic iron in the filtrate 
and passing an electric current through the filtrate. 

501997 July 25, 1893. S. H. EMMENS. Apparatus for the electrolytic extrac- 
tion of metals. In apparatus for the electrolytic extraction of metals, a vat having 
an anode lining on its floor and sides, in comibnation with a suitable cathode or 
cathodes suspended within the vat and a non-porous and non-conducting inner 
wall or curb located between the side linings and the cathode or cathodes and ex- 
tending from the upper surface of the floor lining to above the surface of the electro- 
lyte, and serving to support a lining of the substance to be acted upon in contact 
with the anode side linings and to prevent short-circuiting between said anode side 
linings and the cathodes. 

507130 October 24, 1893. C. HOEPFNER. Electrolytic production of metals. 
The process of obtaining copper and silver free from other metals, which consists 
in forming a cuprous-chloride solution of these metals by leaching a cupriferous 


and argentiferous material with a cupric-chloride solution containing a solvent 
for cuprous chloride, separating from the cuprous-chloride solution so obtained 
such metals as arsenic, antimony, cobalt, and the like, extracting the silver by 
precipitation, electrolyzing the cuprous-chloride solution, preventing the solution 
at the anode from commingling with the solution at the cathode, mixing together 
the two solutions after having been acted upon by the electric current and pre- 
venting an accumulation of iron therein by oxidizing and removing the latter. 

512361 January 9, 1894. p < C. CHOATE. Art of producing metallic zinc. 
The method of producing from an impure solution of zinc salts a zinc electrolyte 
free from depositable impurities, which consists in subjecting the solution to the 
action of an electric current to precipitate and deposit the depositable impurities, 
and at the same time preventing the resolution of such impurities in the solution 
by neutralizing the acid set free in the bath with a neutralizing agent which is free 
from any depositable impurities soluble in the solvent element of the bath. 

512362 January 9, 1894. P. C. CHOATE. Process of preparing solutions 
carrying salts of zinc. The process of forming a solution carrying salts of zinc, 
which consists in forming a sulphate solution of the soluble elements of the ore 
and recovering the same therefrom by evaporation and crystallization, heating 
the crystallized product to drive off the salts of metals more volatile than zinc 
and convert those less volatile than zinc into compounds insoluble in water and 
finally treating the mass with water to dissolve the zinc element. 

518732 April 24, 1894. p - C. CHOATE. Art of producing metallic zinc. The 
process of continuously producing metallic zinc by electrolysis, which consists in 
depositing the zinc from an acidulated solution of a zinc salt, drawing off from the 
bath the free acid liberated therein, dissolving in such acid oxidized zinc, in the 
state of fume, freed from its more volatile soluble impurities, and returning the 
solution thus formed to the bath from time to time, as required, to maintain the 

526099 September 18, 1894. P DANCKWARDT. Apparatus for and process of 
extracting gold or silver from ores. The process of extracting gold and silver from 
ores, which consists in subjecting the same simultaneously to the action of cyanide 
of potassium, an alkali sulphide, and to electrolysis; and the combination of a. 
main apparatus consisting of a revolving outer drum having blades, an insulated 
inner drum and electric connections, with an auxiliary apparatus consisting of a 
series of communicating tanks, rotating insulated drums and electric connections. 

528023 October 23, 1894. L- PELATAN and F. CLERICI. Extracting gold from 
its ore. The combination with a crushing mechanism and an amalgamator, of a 
series of vessels containing a solution of cyanide of potassium and a salt of sodium, 
each vessel having an amalgamated copper bottom connected to one pole of a 
generator of electricity and a central shaft having a zinc pipe and agitator con- 
nected to the other pole, a filter, a series of communicating closed vessels of lead, 
each containing a body of aluminum chips resting on a perforated diaphragm 
above the inlet and rising nearly to the outlet, and means for creating a vacuum 
beneath the filter to drive the fluid through and into the series of lead vessels under 

531169 December 18, 1894. V- ENGELHARDT. Process of extracting metals- 
from sulphide ores, etc. The process of treating the sulphur compounds of metals, 
which compounds have combined therewith other ore compounds not soluble in 
a solution of an alkaline sulphydrate, which consists in extracting the sulphur 
compounds by treatment with an alkaline sulphydrate, thereby also generating 
sulphureted hydrogen, subjecting the solution thus formed to the action of an 
electric current in the cathode compartment of an electrolytic cell, in the anode 
compartment of which is an alkaline chloride, thereby obtaining the metals, reform- 
ing the sulphydrate, and liberating free chlorine, treating the ore residues, result- 
ing from the sulphydrate bath with such chlorine, and subjecting the solution 
thus obtained to the action of the sulphureted hydrogen first generated in the sulph- 
hydrate bath. 

537423 April 9, 1895. F. H. LONG and D C. SKADEN. Apparatus for recover- 
ing precious metals from their ores. An apparatus for recovering precious metals 


comprising a revoluble drum, a perforated metal tube opening from said drum 
and provided with a fabric jacket, a series of plates secured to the inner surface 
of the drum and having inwardly extended blades or flanges, electric connections 
to the plates and tube for rendering the same of opposite polarity, a rotatable 
conveyor located and working in said tube and a fixed vent-pipe passing axially 
through the drumhead and opening into the interior of the drum near the top 

538522 April 30, 1895. E. D. KENDALL. Process of and reagent for recover- 
ing silver and gold from solutions. The process of the recovery of gold and silver 
from solutions, which consists of the following steps: First, the subjecting of the 
ore containing the precious metals to the action of a solvent, thus obtaining an 
aqueous solution of the solvent and the minerals contained in the ore; second, 
subjecting the said solution to the electrochemical action of a mercurial amalgam; 
third, subjecting the valuable precipitate secured by the preceding process to 
the action of dilute acid in the presence of carbon; fourth, the recovery of the 
valuable metal from the result of the preceding process. 

043546 July 30, 1895. E. J. FRASER. Process of and apparatus^ for treat- 
ment of precious metals. The process of separating gold or other precious metal 
held in an electrolytic solution, which consists in passing the solution through 
a vessel containing "alternating porous layers of zinc and carbon, to set up a local 
voltaic action which tends to decompose the solution, precipitating the gold in the 
carbon by filtration. 

543673 July 30, 1895. M. CRAWFORD. Process of extracting precious metals- 
from their ores. The improved process of removing precious metals from their 
ores which consists, first, in lixiviating the ore with a cyanide solution which has 
been subjected to the action of an anode separated from its corresponding cathode 
by a porous partition which substantially prevents the circulation of the electrolyte ; 
second, in withdrawing said solution and removing the precious metals there- 
from; third, in again subjecting the solution to the action of an anode separated 
from its corresponding cathode as before and using it over again in continuous 

543674 July 30, 1895. M. CRAWFORD. Process of extracting precious metals 
from their ores. The improved process of extracting precious metals from their 
ores, which consists in forming a solution of a cyanide and a cyanate of the cor- 
responding base, the total amount of cyanate being not less than 25 per cent, of the 
total amount of cyanide present; lixiviating the ore therewith and extracting 
the dissolved precious metals from said solution. 

543675 July 30, 1895. M. CRAWFORD. Apparatus for extracting precious 
metals from their ores. An apparatus for extracting precious metals from their 
ores, which consists in the combination of a tank wherein the solvent liquid is stored;, 
a revoluble lixiviating receptacle; a pipe running from said storage-tank to the 
lixiviating receptacle; an amalgamating table; means for causing the lixiviating 
receptacle to discharge its contents continuously upon the amalgamating table j 
a separating-tank; means for conducting ore which has passed over the amalga- 
mating table into the separating-tank; means for separating the solid contents'- 
of this separating-tank from its liquid contents; a third tank; connections whereby 
the solvent liquid thus separated is passed to said third tank; means for 
reclaiming the precious metals from the solution in said third tank; and connec- 
tions whereby the solvent liquid is run from the third tank to the storage-tank p 
and a separator for removing the tailings of the ores of precious metals from their- 
accompanying solvent solution, which consists in the combination of a tank into- 
which the ores and solution are discharged; a conveyor running from the bottom, 
of said tank to a point exterior thereto by which the solids are separated from the' 
liquids; a car-filter with a permeable bottom situated below the discharge end 
of the conveyor; and a second tank below said car-filter. 

544610 August 13, 1895. E. W. CLRAK. Process of and apparatus for extract- 
ing ores by electrolysis. In an electric chlorinator for gold ores, the combination 
of the hollow cylinder constructed in longitudinal sections united by bands, and 
having the series of separate boxes or chambers communicating with its interior; 


the electrical connections consisting of the anode in the cylinder chamber, and 
the cathodes in the boxes or amalgamating chambers, the agitator-shaft provided 
with the spirally-arranged series of stirrer-arms and adapted to revolve in the 
cylinder chamber, and the stuffing boxes at the ends of the cylinder. 

546873 September 24, 1895. E. A. ASHCROFT, Process of treating zinc-bearing 
ores. In the treatment of zinc-bearing ores and zinc-bearing products, the method 
of simultaneously depositing zinc from a catholyte free from iron, and raising 
i ferrous-salt solution to the ferric state, which consists in passing the zinc-bear- 
ing solution free from iron, around the metallic cathodes of an electrolytic appa- 
.ratus, and simultaneously passing the ferrous-salt solution around the insoluble 
anodes of the said electrolytic apparatus. 

549907 November 19, 1895. A. L. ELTONHEAD. Apparatus for extracting 
gold. In an apparatus for extracting gold and other metals, the combination of 
a mercury receiving-box, a horizontally movable vessel therein, having its lower 
end open and unobstructed whereby mercury placed within the box may, in seek- 
ing its level, enter said vessel, a horizontally placed anode strip suspended within 
the latter, means for adjusting the strip vertically, a cathode connection and con- 
ductor wires adapted to connect the anode and cathode with a suitable dynamo 
or battery. 

551648 December 17, 1895. L. PELATAN and F, CLERICI. Eletcrolytic process 
-o/ obtaining precious metals, In an apparatus for the extraction of precious metals 
by direct electrolytic action, the combination with an electrolytic vat having 
cathodes arranged at its bottom, of anode cylinders arranged above the said cathodes, 
anode plates alternating with said cylinders, a generator of electricity having its 
poles connected to said anode cylinders and plates and to the cathodes, means 
for rotating the anode cylinders which are provided with agitators, a force-pump 
having injection-pipes to discharge beneath the anode plates and cylinders, said 
pipes being provided at or near their mouths with interior, concentric rods having 
spiral ribs, or feathers, and suction-pipes having their open ends arranged above 
the anode plates. 

552960 January 14, 1896. C. HOEPFNER. Process of producing cuprous 
oxides. The process which consists in leaching cupriferous materials with a cupric- 
chloride solution containing calcium chloride, whereby a solution containing cuprous 
chloride is obtained, converting the cuprous chloride in a portion of the solution 
into cupric chloride by means of a suitable acid as sulphurous acid in the presence 
of oxygen, freeing the other portion of the solution from metals other than cop- 
per, and converting the cuprous chloride therein into cuprous oxide by means of 
a suitable reagent, as caustic lime. 

553816 January 28, 1896. L. PELATAN and F. CLERICI. Process of and 
apparatus for extracting gold from its ores. A single continuous process for the 
extraction of precious metals from their ores, and the amalgamation of the same 
whish consists in treating said ores with a comparatively weak solution of a solu- 
ble cyanide, such as cyanide of potassium, adding thereto a peroxide, such as 
hydrogen binoxide, increasing the electric conductivity of said solution by adding 
-chloride of sodium, increasing the solvent power of said solution by passing a 
relatively weak current of electricity through the same, retaining the sodium 
chloride in the solution practically without decomposition and continuously revolv- 
ing the anode in the solution over a fixed cathode of mercury. 

556092 March 10, 1896. O. FROLICH. Process of extracting noble metals 
from ores. The process of extracting precious metals from a lye containing also 
inferior metals, said lye containing substantially five grains of each of the said 
metals to the pint, which consists in subjecting the said lye to the action of an 
electric current of substantially twelve amperes for each two square yards of cathode 
surface, whereby the gold is separated by electrolysis. 

563143 June 30, 1896. J. DOUGLAS. Process of extracting copper from ores. 
The method of extracting copper from solid cuprous chloride, which consists in 
moistening said solid cuprous chloride with water, inserting both electrodes of an 
electric circuit in the said solid cuprous chloride, and then passing an electric cur- 
rent therethrough. 


56S144 June 80, 1896. J. DOUGLAS. Process of extracting copper from ores. 
The process of extracting copper from the solid cuprous chloride, which consists in 
suspending the said solid cuprous chloride in an acidulated electrolyte, inserting 
the cathode of an electric circuit into the solid cuprous chloride, and the anode 
into the electrolyte, and passing an electric current therethrough. 

566894 September 1, 1896. P. DANCKWARDT. Apparatus for extracting gold 
and silver from ore. The combination of a revolving barrel having an amalgamated 
copper lining with non-conducting bottoms, a series of inclined perforated metal 
strips secured to such bottoms, insulating rings that sustain the bodies of such 
strips, and with electric connections that communicate with the barrel and the 

566986 -September 1, 1896. R. KECK. Cyanide process of extracting precious 
metals from their ores. The process of extracting precious metals from their ores, 
which consists in dissolving said metals in a cyanide solution and extracting them 
therefrom by electrolytic precipitation effected by alternating plates of lead and 
aluminum, the former being anodes and the latter cathodes. 

567503 September 8, 1896. L. PELATAN and F. CLERICI. Process of extracting' 
gold and silver from their ores. The process, which consists in submitting the ores 
of gold and silver to the action of a comparatively weak cyanide solution con- 
taining chloride of sodium, intensifying the solvent power of the solution by the 
passage of a continuous electric current having an electromotive force below 
that required for the decomposition of sodium chloride and continuously revolving 
the anode from which the current is supplied to the solution over a mercury cathode. 

568099 September 22, 1896. L. PELATAN and F. CLERICI. Electrolytic appa- 
ratus for extracting gold and silver from their ores. The combination with a vat 
having a flat bottom, of a cathode of mercury spread thereon, an anode laving v, 
the form of an endless belt, rolls arranged near the ends of the vat to support and 
give continuous movement to said anode in parallelism with the surface of the 
cathode, and means for imparting continuous movement to said anode, in one 
direction, it being provided with stirring devices moving with it. 

568724 October 6, 1896. E. ANDREOLI. Apparatus for electrodeposition of 
gold or silver. In an apparatus for the electrodeposition of gold and silver from 
a solution, a tank provided with one or more anodes and a series of amalgamated 
cathodes, each cathode consisting of perforated, skeleton, or network plates and 
a layer of mercury in the bottom of the tank into which each of the cathodes dips,, 
said layer of mercury being connected with the negative pole of electricity, thereby 
constituting a common vehicle for the current from all the cathodes while at the- 
esame time maintaining the said cathodes constantly amalgamated. 

568741 October 6, 1896. H. R. CASSEL. Process of extracting gold frcm sub- 
stances containing it. The process of extracting gold from ores,_ which consists in 
decomposing a bromide of an alkaline base by electrolysis, dissolving the gold \(\ 
by the anode solution, adding the cathode solution, running the product through 
a mixture of iron and carbon to precipitate the gold, and redecomposing the liber- 
ated bromine solution by electrolysis. 

568843 October 6, 1896. V. ENGELHARDT and A. NETTEL. Process of treat- 
ing metallic sulphides, The process of treating a metallic sulphur compound, which 
consists in first converting the said compound into a soluble double sulphide by 
treating it with any suitable reagent, such as the sulphydrate of calcium in aque- 
ous solution; then decomposing the resulting solution by electrolysis to produce 
the metal and sulphureted-hydrogen gas, then treating the spent solution with 
carbonic-acid gas to precipitate a carbonate of the base and liberates ulphureted- 
hydrogen gas, then recovering the oxide of the reagent and the carbon ir-aoid 
gas from the precipitate by calcination, then combining the sulphureted-ln drogen 
gas given off during the process with the said oxide to form more reagent, and 
using the recovered carbonic-acid gas to treat more spent solution. 

571468 November 17, 1896. T. P. BARBOUR. Process of treating ores. The 
process of treating ores, which consists in first treating the raw material with 
copper oxide and sulphuric acid, then chlorinating the pulp thus treated, intro- 
ducing the chlorinated mass into a suitable agitator having zmc therein, and estab- 
lishing an electric current through the mass in the presence of zinc; and a chlor- 



inating-tank for treating ores consisting of a revoluble cask having a single man- 
hole and a circular series of bungholes, copper pole disks secured within the cask 
at opposite ends thereof and arranged in an electric circuit, insulator bracing 
p_osts arranged between said disks and the outer heads of the tank, flanged guide- 
rings encircling said cask at an intermediate point, spur-rings encircling the cask 
.near its opposite ends, and a horizontal drive-shaft carrying guide-rolls engaging 
.said flanged guide-rings and drive-pinions engaging said spur-rings. 

573233 December 15, 1896. M. NETTO. Process of precipitating precious 
metals from their alkali-cyanide solutions. The process of precipitating silver and 
gold from their alkali-cyanide solutions, which consists in acidulating the alkali- 
cyanide solution containing said metals with hydrochloric acid so as to precipi- 
tate silver chloride, separating said silver chloride by filtration, subjecting the 
acid filtrate to the action of the electric current so as to deposit the gold on the 
cathode, and regenerating the cyanide solution by the addition of caustic alkali. 

578171 March 2, 1897. C. T. TURNER. Electrolijtical apparatus .An elec- 
trolytic apparatus, provided with an anode consisting of a non-conducting recep- 
tacle coated with an anti-corrosive substance and provided with an outer coat- 
ing of a conducting material and means for connecting said outer coating with 
the positive pole of a source of electrical supply. 

579872 March 30, 1897. J. H. HAYCRAFT. Process of treating auriferous 
and argentiferous ores. The process of treating ores consisting in introducing 
the ore into a pan, adding thereto mercury and soluble salts capable of yielding 
chlorine by electrolysis, raising the ore contents of the pan to about the boiling- 
point of water and passing a current of electricity through the heated mass while 
stirring the same to secure a simultaneous electrolytic chlorination and electro- 
amalgamation, and maintaining the anode out of vertical alignment with the 
mercury cathode. 

581160 April 20, 1897. H. HIRSCHING. Process of treating ores containing 
silver and gold. The process of treating ores, which consists in subjecting them 
in the presence of moisture to the action of ammonia and a nitrate, and then pre- 
cipitating the metal or metals from the resulting solution. 

582077 May 4, 1897. E. MOTZ. Apparatus for extracting precious metals. 
In an apparatus for extracting precious metals, the combination of a rotative 
drum provided with a manhole and having a valved connection for the admission 
of compressed air, a core of insulating material mounted to turn in the said drum, 
metal plates forming the positive and negative electrodes of an electric circuit 
and arranged respectively on the drum and core, and an electrical connection 
for said plates on the core, the said connection being arranged to lock the drum 
and core together. 

584242 June 8, 1897. P. G. SALOM. Process of making commercial lead 
from lead ore. The process of converting lead ore into commercial lead, without 
the application of heat, by subjecting the ore to the action of nascent hydrogen, 
electrolytically developed, producing thereby a spongy mass, and afterward, while 
the mass is in a non-oxidized condition, applying a consolidating pressure. 

685355 June 29, 1897. C. A. BURGHARDT and G. RIGG. Process of obtain- 
ing metallic zinc and copper from ores. The improved process of recovering metallic 
zinc and metallic copper from cuprous zinc ore, which consists in treating the roasted 
and ground ores with an ammoniacal solution, then in freeing the resultant liquid 
from iron dissolved by said solution, then in depositing the metallic copper on 
suitable metallic plates acting as a couple, and in finally effecting the electrolytic 
deposition of the metallic zinc. 

585492 June 29, 1897. J. F. WEBB. Method of an apparatus for separating 
precious metals from their solvent solutions. The improved method of separating 
precious metals from a solvent solution containing the same, consisting in passing 
the solution alternately through a body of carbon and zinc, and subjecting the 
same in its passage to an air current; and a metallurgical filter for this purpose 
vcontaining the same, consisting of a series of alternate compartments, or recep- 
tacles, containing, respectively, carbon and zinc, through which the. solvent solu- 


tion is passed with an upward and downward flow, and electric circuit completing 
connection between the zinc and carbon. 

588076 August 10, 1897. B. MOHR. Process of treating sulphide ore. The 
process for treating sulphide ore by acting on the pulverized ore with acid sodium 
or potassium sulphate, so as to obtain a solution of sulphate of zinc, depositing 
the zinc by electrolysis and thus recovering the acid alkali sulphate, and treating 
the insoluble residue obtained by the lixiviation for recovery of the other metals. 

588740 August 24, 1897. B. BECKER. Apparatus for treating gold and silver 
ores. In apparatus for the treatment of gold and silver ores the combination 
of a vat provided with amalgamating plates and adapted to contain cyanide of 
potassium, in solution, and the ore to be treated, a vat containing the electrodes 
of an electrolytic apparatus and means for causing the circulation of the cyanide 
of potassium solution through the amalgamating vat, and for distributing it in 
the electrolytic vat. 

590801 September 28, 1897. W. L. BROWN. Process of treating rebellious ores. 
The process of treating ores finely divided and mixed with water, which consists 
in adding a suitable compound to said ores and water, which compound contains 
an element which has a chemical affinity for the base constituents of the ore, then 
passing an electric current through said material to unite the said element chem- 
ically with the base constituents and to liberate the precious metals, then cir- 
culating the material over an amalgamated surface which is not in the electrical 
circuit, and finally returning the material again through the field of electrolytic 

592055 October 19, 1897. E. C. KETCHUM. Process of treating ores. The 
process of treating mixed sulphide ores containing lead and zinc, which consists 
in first roasting the ores, then subjecting the roasted ores to the action of a solu- 
tion of caustic alkali in the presence of heat to remove from the ores the lead and 
the zinc, then subjecting the caustic solution containing the lead and zinc to 
electrolytic action in one or more cells to remove the lead, the anodes of which 
cells are immersed in a volume of pure caustic solution, which is separated 
by a porous medium from the electrolyte containing the lead and zinc, and then 
subjecting the caustic solution or electrolyte containing the zinc only to electrolytic 
action in one or more cells to remove the zinc. 

592973 November 2, 1897. E. MOTZ. Electrolytic apparatus. In an elec- 
trolytic apparatus the combination with a frame or sluice of a series of convex 
cathode plates located in the bottom of said frame or sluice, a series of anode plates 
having curved under faces and disposed above said cathode plates, blocks secured 
to the anode plates and supported in the frame or sluice, each block having a recess 
in its upper edge, a series of conductors connected with said anode plates and 
terminating in said recesses in. the blocks, a conducting rod disposed in said recesses 
on the first-mentioned conductors and having a notch therein, a cross-bar passing 
through said notch, a conductor with which said cross-bar is electrically connected, 
locking devices for securing the cross-bar to the frame or sluice, and a conductor 
connected with the cathode plates. 

594611 November 30, 1897. S. H. EMMENS. Process of and apparatus for 
removing^ zinc from zinciferous ores. The process of treating zinciferous ores, which 
consists in pulverizing and roasting the ore, leaching it in a series of vessels through 
which the solution flows continuously, and subjecting the contents of each vessel 
intermittently to electrolytic action, whereby the solution is rendered alternately 
acid and neutral or more acid and less acid in contact with each body of ore; and 
an apparatus for treating zinciferous ores, comprising a series of leaching-vats, 
each provided with an inlet-pipe extending to the bottom and with an exit-pipe 
or trough leading from the top of the vat, and each provided at bottom with an 
insoluble anode, a series of movable cathodes suspended above said vats, means 
for raising and lowering the cathodes of adjoining vats alternately, and an electric 
circuit to the respective poles with which said anodes and cathodes are connected. 

597820 January 25, 1898. N. S. KEITH. Art of obtaining gold and silver 
from auriferous and argentiferous materials. The process of obtaining a precious 
metal from its ores, which consists first in dissolving the gold or silver in a cyanide 
solution containing cyanide of mercury and free cyanide of an alkaline metal, such 


as cyanide of potassium, and then passing a current of electricity through said 
solution to a metallic cathode, whereby an easily removable layer of the precious 
metal and mercury is simultaneously deposited upon said cathode. 

598193 February 1, 1898. E. ANDREOLI. Apparatus for electrodeposition of 
gold and silver. In apparatus for the electrodeposition of gold, silver, or other 
metals, anodes of peroxidized lead acting in the presence of and in combination 
with a cyanide or cyanide-compound solution. 

600351 March 8, 1898. E; A. ASHCROFT. Treatment of metalliferous ores 
and products. The improved process of preparing a solution suitable for leaching 
zinc-bearing ores of zinc-bearing products, consisting in electrolyzing a zinc-bear- 
ing solution successively in contact with a suitable cathode and an anode result- 
ing from the preliminary furnace treatment of products or ores containing cop- 
per and iron, and then depositing the copper from the resulting ferrous solution, 
and simultaneously raising the iron content of such solution to the ferric state 
by electrolyzing the said resulting ferrous solution successively in contact with 
suitable cathodes and insoluble anodes. 

601068 March 22, 1898. F. W. WHITRIDGE. Method of and apparatus for 
extracting gold from its ores. The method of extracting gold from a weak cyanide 
solution, which consists in circulating the solution over anodes of iron and cathodes 
of lead, said cathodes being formed of thin plates arranged at short distances apart 
and having from 9 to 10 square meters of surface for each ton of solution in con- 
tact with them; and subjecting the said solution while in motion to an electric 
current of from 3.5 to 4 volts, and of from 0.5 to 1.5 amperes per square meter 
of cathode surface; and in apparatus for^ obtaining gold from a weak cyanide 
solution by electrolysis, the combination with a cell provided with anodes of iron 
and cathodes of lead formed of thin plates, said cathode plates having from 9 to 
10 square meters of surface to each ton of solution in the cell; of means for cir- 
culating the solution in the cell, and means for subjecting the solution to a weak 
current of electricity. 

60390 1 May 10, 1898. J. R. HEBAUS. Apparatus for extracting precious 
metals. An apparatus for extracting precious metals from their ores, comprising 
a tank having an amalgamated copper lining forming a cathode and a multiplicity 
of agitators, each rotating on its own axis and at the same time traveling around 
the tank, the said agitators forming an anode and an electric circuit. 

605835 June 21, 1898. E. and G. ANDREOLI. Electrolytic production of amal- 
gams, etc. An apparatus for the production of amalgam, consisting of a cell pro- 
vided with positive and negative compartments separated by porous diaphragms, 
the negative compartments having a raised middle portion in the form of a table 
or block between the sides of which and the said partitions are narrow vertical 
spaces, the top of the block or table and the vertical spaces being covered and 
filled with a continuous body of mercury forming a cathode. 

614572 November 22, 1898. J. C. McNuLTY. Method of and apparatus for 
treating ores. The art of extracting precious metals from their ores, consisting 
in mixing pulverized ore with an electrolytic fluid, causing the mixture to flow 
from one level to another between adjacent electrode plates of opposite polarity, 
passing an electric current between said plates and vibrating the electrodes in a 
direction substantially at right angles to the plane of said electrodes for the pur- 
pose of preventing the polarization thereof; and in apparatus for the electro- 
lytic treatment of ores the combination of a plurality of vats arranged in 
pairs communicating at the top, adjacent electrode plates of opposite polarity 
suspended within said vats and connected with a source of electricity, vibratory 
supports for said electrodes, means for vibrating the same at substantially right 
angles to their planes, a pressure conduit for pulp leading to the bottom of the 
first vat to provide an upward current therethrough, and an exit at the bottom 
of the succeeding vat providing a discharge for the downward current of pulp 
overflowing from the top of the vat preceding. 

616891 January 3, 1899. G. D. BURTON. Electrolytic apparatus for treating 
metals and ores. In an electrolytic ore-treating apparatus, the combination of a 
tank for containing an electrolyte, an anode disposed in said tank, a cathode dis- 


posed in said tank, a screen or deflector also disposed in said tank between the 
anode and cathode and adapted to distribute the ore or material being treated, 
said screen having a conductive surface connected to the negative pole of an elec- 
tric source whereby it is adapted to collect a portion of the product reduced from 
the ore by the action of the current and the electrolyte. 

617911 January 17, 1899. E. A. SMITH and M. H. LYNG. Method of extract- 
ing metallic ores. The wet process of extracting copper from its ores having pre- 
cious metal therein, which consists in digesting the pulverized ore under action 
of heat and an oxidizing agent, in presence of sulphuric acid, exposing the dis- 
solved sulphates to metallic copper for precipitation of the silver, treating the 
filtrate electrolytically to deposit the copper, evaporating the lean electrolyte to 
concentrate the free acid, and crystallize the metallic sulphates, and finally cal- 
cining such crystallized sulphates to properly regenerate them as oxidizing agents 
for reuse. 

623822 April 25, 1899. L. PELATAN. Apparatus for treating ores or the 
like. In apparatus, the combination with a circular vat, of a revolving anode, 
situated above and parallel to a mercury cathode, with an unobstructed space 
above the surface of the cathode, the said anode having arms which extend close 
to the peripheral wall of the vat and are suspended from a shaft, and are pro- 
vided with pins or stirrers projecting upward and downward to within a short 
distance of the underlying cathode, and projections or baffles extending inwardly 
from the inner surface of the peripheral wall of the vat. 

626972 June 13, 1899. T. CRANE Y. Electrolytic apparatus for deposition 
of metals from solution. In an electrolytic apparatus, the combination of an outer 
tank provided with suitable feed and discharge connections for the liquid into 
the bottom and top, respectively, and an electrolytic couple, composed of sheet 
or analogous electrodes each folded in a fabric, with oppositely projecting mar- 
ginal portions and rolled together into a tight bundle and sealed in the tank, whereby 
the fabric inclosing the electrode forms a porous medium through which the elec- 
trode is compelled to flow. 

627442 June 20, 1899. L. PELATAN. Process of electrolytically treating ores. 
The improvement in processes of treating ores electrolytically, consisting in add- ^>y* 
ing to a sludge, consisting of ore and water, a solvent and picric acid as an oxi- 
dizing agent and then passing an electric current therethrough. 

631040 August 15, 1899. J. E. GREEN AWALT. Process of extracting precious 
metals from their ores. -A process for the treatment of gold and silver ores which 
consists, first, in properly roasting the pulverized ore; second, placing the ore Jf 
in a filtering-vat; third, washing the ore to remove soluble salts; fourth, in pass- (T) 
ing through the ore an electrolyzed solution consisting of a solution of chlorides 
chiefly sodium and ferric chlorides with a small percentage of bromides and 
small quantities of chlorine, bromine, and hypochlorous acid, with such other 
compounds as result from the electrolysis of a chloride and bromide solution; fifth, 
passing the solution after it leaves the ore through a precipitating-tank ; sixth, 
passing the solution after it leaves the precipitating-tank through the positive 
or onode compartment of an electrolytic cell, keeping the solution separate and 
distinct from the solution in the negative or cathode compartment of the cell; 
and, seventh, returning the solution from the regenerating cell to the ore in the 
vat and passing it thence to the precipitating-tank, again to the regenerating cell, 
arid again to the ore as often as may be required to effect the necessary saving 
of the values. 

633544 September 19, 1899. H. S. BADGER. Electrolytic apparatus for pre- 
cipitating metals. A precipitating-tank comprising the tank body, having a mer- 
cury-coated surface in its bottom, a re voluble shaft suspended in the tank and 
provided with hollow arms having perforations on their lower sides to deliver 
air or vapor in proximity to the said surface, means for rotating the revoluble 
devices, means for introducing air or vapor to the hollow arms, and an electric 
circuit in which the shaft, agitating arms, and mercury-coated surface are located. 

639766 December 26, 1899. L. E. PORTER. Apparatus for extracting precious 
metals from ores. The combination of a rotatable barrel adapted to form the 


cathode; a porous lining of non-conducting material arranged inside the barrel; 
a lining of filtering material arranged inside the non-conducting lining; anode 
plates arranged inside the filter lining; a source of electrical energy, having one 
pole connected with the barrel and the other pole connected with the anode plates. 
640718 -January 2, 1900. C. P. TATRO and G. DELIUS. Process of extracting 
precious metals. In the process of separating precious metals from ores, the steps 
comprising electrolytically depositing a portion of the precious metals in the bath 
upon a drum cathode revolving partially immersed in the bath, at the same time 
scraping the said deposit from the drum, also simultaneously depositing other 
portions of similar precious metals in the same bath upon a cathode of sodium 

641571 January 16, 1900. W. WITTER. Process of producing solution of 
cyanogen halide. The process for producing a solution of cyanogen halide by 
electrolyzing in a bath without a diaphragm and with inert electrodes a solution 
containing an alkali cyanide, an alkali halide, and the salt of' a metal which forms 
an insoluble hydroxide. 

649151 May 8, 1900. W. WRIGHT. Apparatus for extracting metals from 
refractory ores. An apparatus for extracting metals from refractory ores, com- 
prising a tank for receiving a sludge of such ores; a stationary, horizontal per- 
forated partition in said tank, fcrming beneath it a chamber; a cathode on the 
bottom of the tank within said chamber; a filtering medium carried on the par- 
tition; a number of pins arranged in a series of concentric circles projecting upward 
from said partition; a main driving-shaft; a series of radial arms supported by 
said shaft, and a plurality of anodes carried by said arms and working between 
the series of concentric pins. 

650646 May 29, 1900. F. H. LONG. ^ Apparatus for electrolytic reduction of 
ores. An electrolytic apparatus, the combination with a reducer vessel; its bot- 
tom cathode and a diaphragm above said cathode, of a set of dependent anodes, 
each consisting of a carbon head; a copper stem extended therefrom through 
the vessel; an incasing iron tube carried by the vessel head to sustain the anode 
pole; a vulcanite sheath for said tube, and suitable elastic gaskets to expansively 
close the joints. 

653538 July 10, 1900. N. L. TURNER. Electrolytic apparatus. An electro- 
lytical apparatus, comprising a tank, rotary agitators located therein eccentrically, 
a series of electrodes whose main portion is concentric with the tank, while the 
portions adjacent to the agitators are curved concentrically with the axes of said 
agitators, and electrodes of opposite polarity to those first named. 

654437 July 24, 1900. W. A. CALDECOTT. Method of extracting gold from 
cyanide solutions containing the preciou.s metals. Means for extracting gold from 
cyanide solutions in depositing cells, consisting in a mechanical mixture of zinc 
shavings and lead shavings. 

656305 August 21, 1900. W. STRZODA. Process of electrolytically extracting 
zinc from ores. The process of electrolytically extracting zinc from its ores, which 
consists in placing the disintegrated or pulverized ore in its natural state in an 
electrolytic vat containing an aqueous alkali-metal solution capable of dissolving 
the cre^ with production of a zincate and in direct contact with the cathode, and 
closing the circuit through the vat, thereby precipitating zinc and the alkali metal 
at the cathode, the alkali metal reacting with the water to regenerate the solvent 

657032 August 28, 1900. A. M. ROUSE. Apparatus for electrolyzing ores. 
In an apparatus of the class described having an anode and a cathode suitably 
arranged therein, the combination of a tank having an outer compartment, a 
tube located therein having an open upper end and provided at its lower end with 
openings forming communication from said compartment, a driving-shaft pro- 
jecting within said tube, an inner cup carried by said shaft, wings carried by said 
cup, an outer cup carried by said wings, a discharge duct, and a valve arranged 
to close said duct. 

662286 November 20, 1900. E. MOTZ. Electrolytic apparatus. In an elec- 
trolytic cell having open ends, the combination with a removable cross-bar and 


means for supporting it in position, of a metallic plate covering the bottom and 
two sides of the bar, and forming the anode plate of the cell, of a metallic plate 
arranged horizontally below and parallel with the bottom of the cross-bar, so as 
to form a passage between such plate and the bottom of the cross-bar, suc^i plate 
forming a cathode plate of the cell, and an auxiliary metallic cathode plate arranged 
vertically and parallel with the sides of the cross-bar and in circuit with the hori- 
zontal cathode plate, such vertically arranged plate extending below the plane 
of the bottom of the cross-bar, so as to more or less obstruct the said passage. 

664537 December 25, 1900. J. DOUGLAS. Process of extracting copper. The 
process of reducing copper ore and matte, which consists in electrolyzing solid 
cuprous chloride, employing the gases evolved in the treatment of copper ore and 
matte, employing the electrolyte resulting from the electrolyzing of the solid cu- 
prous chloride as a solvent for the cuprous chloride so produced, and recovering 
the copper from the solution by electrolysis. 

668842 February 26, 1901. A. M. ROUSE. Apparatus for electrolytically 
extracting and depositing gold and silver from their ores. In an apparatus, the com- 
bination of a series of pulp-receiving tubs, anodes and cathodes arranged in said 
tubs, an agitation-tube having communication with said tubs at their upper and 
lower ends, an agitator arranged in said tube, perforated conduits located in the 
upper ends of said tubs, chutes located beneath said conduits onto which the ore 
pulp is discharged, and deflectors located beside said conduits adapted to direct 
the flow of pulp onto said chutes as it passes through said conduits. 

669752 March 12, 1901. P. W. KNAUF. Electrolytic apparatus. An element 
for an electrolytic series, consisting of a metallic receptacle having its lower por- 
tion of less diameter than the upper portion and having a bottom surface which 
is inclined upward radially from the center to the outer periphery, in combination 
with an exterior peripheral seat arranged below the upper edge, and an orifice 
adjacent to said seat. 

669926 March 12, 1901. C. HOEPFNER. Process of electrolytical extraction 
of metals. A process which consists in placing a soluble metallic anode in a solu- 
tion capable of dissolving the same, placing a suitable cathode in a second similar 
solution containing a metal more electropositive than that of the anode, inter- 
posing a third similar solution of less solution pressure between the two first men- 
tioned, placing an auxiliary cathode therein, separating the solutions by suitable 
diaphragms, maintaining the solutions in motion and at a temperature above 
normal, passing a current, thereby dissolving the anode and precipitating the 
cathode metal at the cathode, and part of the diffused anode metal at the aux- 
iliary cathode, precipitating the anode metal from the anode and intermediate 
solutions and returning the resulting solution when enriched in cathode metal 
to the cathode cell. 

678526 July 16, 1901. C. P. STEWART. Apparatus for the recovery of gold 
from cyanide solutions. An apparatus for recovering precious metals from flowing 
cyanide solutions, comprising in combination a relatively long substantially hori- 
zontal trough, means for supplying the solution at one end thereof, a partition 
near the receiving end of the trough for distributing the solution, a retaining 
partition at the discharge end of the trough adapted to retain the solution in the 
trough to the desired height, a body of quicksilver in the bottom of the trough 
between said partitions, a series of transverse anode supports extending substan- 
tially from partition to partition, a series of anodes adjustably mounted in said 
supports and extending down into the path of the flowing solution, and suitable 
electric connections. 

682155 September 3, 1901. C. P. TATRO and G. DELIUS. Electrolytic appa- 
ratus for extracting precious metals. In apparatus for extracting precious metals, 
a tub: a mercurial cathode in the bottom thereof, a principal anode, means for 
lowering it into and raising it out of the tub, and a minor anode permanently in 
the tub. 

689018 December 17, 1901. W. ORR. Method of recovering cyanides. The 
method of regenerating cyanide solutions which have become fouled by the pres- 
ence of zinc and copper contained in the solutions, as double cyanide of zinc and 


copper with the alkaline metals which consists, first, in passing through the solu- 
tion from a series of zinc anodes to a corresponding series of metallic cathodes 
a current of electricity; next, in introducing into such solution alkaline hydrate, 
being hydrate of the monovalent alkali metals and hydrate of the divalent alkali 
metals in the proportion of about two to one; next introducing into the solution 
a soluble alkali -metal sulphide, and finally removing the resulting zinc-sulphide 

689674 December ?4i 1901. A. I. IRWIN. Machine for extracting metal from 
ores. In a machine for the automatic and continuous extraction and deposition 
of metal from ores at one and the same time, a treatment-tank, an endless anode 
traveling in s?id tank, the upper and lower stretches of the anode being in posi- 
tion to be immersed in the solution in the tank, diagonally disposed blocks of 
insulating material attached to said anode, cathodes in the tank, one under each 
stretch of trie anode, and connections with a source of electricity. 

689959 December 31, 1901. E. L. GRAHAM. Process of disintegrating and 
comm,invting minerals or ores. The process of treating ores, consisting of the fol- 
lowing steps: First, immersing the ores in a solution of sulphuric and hydrofluoric 
acids incapable of dissolving the ore; second, passing an electric current of suffi- 
cient strength to disintegrate the ore through the solution; and third, extracting 
the metal from the ore. 

699964 May 13, 1902. F. H. LONG. Electrolytic converter. In electrolytic 
converters, the combination with the closed reducer vessel having the anode and 
cathode terminals and the' interposed diaphragm dividing the vessel into upper 
anode and lower cathode chambers, of a combined separator and vent-pipe con T 
nected to the cathode chamber beneath the diaphragm extending upwardiy above 
the level of said diaphragm and having a free outlet for the gases. 

700941 May 27, 1902. N. S. KEITH. Process of treating copper or other 
ores for obtaining their contents of metals. The process of electrolyzing a solution 
of a metal; to deposit the metal therefrom, which consists in passing it as an elec- 
trolyte through a succession of two or more electrolytic cells, arranged so that 
the cells are connected in electrical series with a source of electricity; the anodes 
insoluble, the electrodes of each cell in electrical multiple, and having gradually 
increasing surfaces, whereby there is a gradual reduction of the current density 
as the metal of the electrolyte is deposited. 

704639 July 15, 1902. C. HOEPFNER. Leaching and extraction of metals 
from their ores. The process of extracting metals, which consists in leaching a 
suitable material containing copper, lead, and silver, with a warm cupric-chloride 
solution containing a solvent of cuprous' chloride, in quantity less than is required 
for saturation, thereby dissolving lead and silver chlorides, precipitating them, 
reconverting the solution into cupric chloride, using the same for leaching fresh 
quantities of ore, leaching the residues with a similar hot solution more concen- 
trated in cupric chloride, thereby dissolving copper and recovering those metals 
therefrom, reconverting the resulting solution into cupric chloride, and returning 
the latter into the cycle of operations. 

706436 August 5, 1902. F. T. MUMFORD. Apparatus for the electrolytical 
treatment of ores or sfimes. An apparatus for the extraction of metals from their 
ores and slimes, comprising a rotatable cylindrical metallic drum, a copper lining 
therein, a body of mercury in the drum to maintain the lining amalgamated, a 
valve-controlled inlet and outlet, and a relief- valve at one end, a plurality of con- 
ductive rods insulated from and passing longitudinally through the drum, a metallic 
ring connecting the bars, trailing electrical contact for the drum and one for said 

709817 September 23, 1902. C. E. DOLBEAR. Ehctrolytically treating ores. 
The method of reducing metals from their ores, which consists in dissolving the 
crushed ore in a compound containing a nitric acid radical, adding to the mix- 
ture sulphuric acid, and subjecting the resultant compound to the action of an 
electric current. 

725864 April 21, 1903. W. B. MCPHERSON. Apparatus for the treatment of 
gold or other ores. A precipitating apparatus for d^po^iting gold and silver from 


a cyanide of potassium solution and from other chemical solutions, comprising 
a precipitating-box having downward, inclined bottom with openings therein, 
valves located in said openings, said box provided with a series of electric con- 
ducting plates vertically arranged therein and connected with a source of electric 
supply, a gauge receptacle, a pipe communicating with said receptacle and with 
the precipitating-box through which the said solution passes back and forth, a 
float within said receptacle and adapted to reciprocate therein, a yoke secured 
to said float, a horizontally reciprocating valve-rod, devices for connecting said 
yoke with said valve-rod, means for operating said valves in connection with valve- 
rod, arid means for conveying said solution from said precipitating-box and return- 
ing the same thereto. 

737554 August 25, 1903. L. P. BURROWS. Electrolytic apparatus. An 
electrolytic apparatus, comprising a dissolving vessel having a revoluble anode, 
a depositing vessel having a cathode, means for conveying an unbroken stream 
of liquid from the dissolving vessel, and an electric circuit including said anode 
and cathode, whereby the electric current is caused to transverse the stream of 
liquid flowing from the dissolving vessel into the depositing vessel. 

741231 October 13, 1903. W. H. DAVIS. Process of treating cyanide solu- 
tions. The process for treating cyanide solutions during or subsequently to their 
contact with the ore, consisting in introducing into the solution an alkaline hydrate 
and then subjecting the mixture to the action of an alternating electric current, 
thereby raising the osmotic pressure to dissociate the double salts in the solution, 
causing precipitation of the hydrates of the base metals and to combine the freed 
cyanogen with the alkaline hydrates to cause simultaneous regeneration of the 
cyanide in the solution and clarifying of the latter. 

741439 October 13, 1903. C. E. BAKER and A. W. BURWELL. Process of 
treating ores. The process of recovering copper and nickel from a solution of sul- 
phates of copper, nickel, and iron, which consists of electro-depositing the copper, 
neutralizing the solution, and electro-depositing the nickel with a current density 
insufficient to deposit the iron. 

743668 November 10, 1903. R. SUCHY and H. SPECKE'TER, Extracting 
chromium from chrome-iron ore. The process of making soluble chrome-iron ore 
and obtaining chromium compounds, which consists in heating the ore together 
with sulphuric acid in excess and an oxidizing agent and separating by filtration 
the precipitated insoluble ferrisulphate from the chromosulpho acid. 

749843 January 19, 1904. H. R. CASSEL. Process of extracting precious 
metals by electrolysis. The process of extracting precious metals by electrolysis, 
which consists in circulating the pulp between vertical electrodes, amalgamating 
a vertical cathode, successively deflecting the rebounding mercury back upon 
said cathode, removing the amalgam, neutralizing the alkali in the mercury, and 
returning the mercury to the cathode. 

749844 January 19, 1904. H. R. CASSEL. Apparatus for extracting precious 
metals by electrolysis. An apparatus for extracting precious metals by electrolysis, 
comprising a tank, inclosed vertical electrodes, mercury deflectors, and pulp-guards 
at the sides of the cathode, an elevated pulp-box, communicating perforated launders, 
means for lifting the pulp into said box, an elevated mercury pot, communicating 
slidable perforated troughs, and means for lifting the mercury into said pot. 

755302 March 22, 1904. E. A. LE SUEUR. Extraction of copper from com- 
minuted mineral mixtures, The method of obtaining metallic copper from mix- 
tures containing it, which consists, first in treating said mixtures with an ammo- 
niacal solution, containing a cupric compound or compounds, so as to dissolve 
the desired copper, then in removing a portion of the total copper contents of 
the solution, and lastly in using the partially exhausted solution over again to 
dissolve fresh copper as before. 


Acetonitrile, 40 

Adler's process, hydrocyanic acid, 93 

Albright's process, sulphocyanide, 285 

Alcoholic carbimides, 40 

Allyl cyanide, 40 

Aluminium cyanide, 24 

Ammonium cyanate, 37 

cyanide, 23 
cyanhydrate, 60 
sulphocyanate, 274 

thiosulphocarbamate, 273 
Ammoniacal liquors, 224 

cyanogen from, 242 
Prussian blue, 292 
Amyl cyanide, 40 

Andreoli's process, gold precipitation, 315 
Antimony blue, 293 
Apparatus, Bueb's, 186-8 

Castner's, 142, 174 

Engler's, 201 

Mackey's, 136 

Raschen's, 99 

Stassfurter Chem. Fabrik, 159 

Roca's, 167 

Arnpul, Camille, works of, 248 
Auriferous minerals, oxidation of, 295 
Auripotassic cyanide, 35 
Aurocyanide, 35 
Aurosopotassic cyanide, 35 
Azulmic acid, 11 

Barium cyanide, 24, 169 
ferricyanide, 32 

Beck's process, ferricyanide, 266 
Beilby's process, cyanide, 162 
Bergmann's process, hydrocyanic acid, 94 

cyanide, 101 
results, 154 

Beringer's process, cyanide, 150 
Berthelot's hypothesis, 7 
Black-mass, composition of, 204 
Blackmore's process, cyanides, 150 
Blood-lye, 81 
Blue potash, 205 

Bouxvillers Mines' process, ferricyanide, 

Bower's process, cyanide, 107 

ferrocyanide, 243 

British Cyanide Co.'s process, cyanide, 105 

nide, 283 

Brock's process, sulphocyanide, 282 
Brunquell's process, cyanide, 153 

ferrocyanide, 210 
Bueb's apparatus, 186 

process, cyanide, 185 

ferrocyanide, 237 

Buignet's method, hydrocyanic acid, 48 
Burchell's method, 52 
Butyl cyanate, 40 
cyanide, 40 
Butyro nitrile, 40 

Calcium cyanide, 24 

ferricyanide, 32 

sulphocyanate, preparation of, , 


Carbazol, 183 
Carbylamines, 39 
Castner's process, cyanide, 153 
Cetyl cyanide, 40 
Chaster' s process, cyanide, 165 

hydrocyanic acid, 88 
Chem. Fabrik Aktiengesellschaft's process, 

cyanide, 165 

Chlorides, detection of, 47 
Chlorine process, ferricyanides, 261 
Chromium cyanide, 25 
Chryseane, 21 
Clark's process, 16 

Clauss and Domeier's process, ferrocya- 
nide, 234 
Coal, nitrogen content of, 220 

types of, 216 
Cobalt cyanide, 27 

ferricyanide, 32 

Cobalticyanide of potassium, 34 
sodium, 34 




Cobaltocobalticyanide, 34 

Coke, elements of, 218 

Compagnie Generate des Cyanures, 273 

Conroy's process, cyanide, 108 

ferrocyanide, 211 
Cooling-mixture, 329 
Copper cyanide, 26 

ferricyanide, 32 
Crystallization, 210 
Cyanamid, 147 
Cyanate of ammonium, 37 
silver, 37 
sodium, 37 
Cyanates, 44 

detection of, 47 
Hertig's method, 47 
Cyanic acid, 36 

esters, 40 

Cyanide of aluminium, 24 
ammonium, 23 
barium, 24 
calcium, 24 
cobalt, 27 
copper, 26 
chromium, 25 
gold, 27 
iron, 25 
manganese, 25 
mercury, 26 
nickel, 27 
platinum, 27 
silver, 26 
sodium, 23 
tin, 25 
zinc, 24 

'Cyanides, analysis of commercial, 47 
characteristics of, 328 
critical temperatures, 324 
density of, 323, 329 
determination of medicinal, 


double, 28 
extraction from illuminating 

gas, 214, 219 

extraction from purifying ma- 
terials, 245 
extraction from sulphocya- 

nides, 95 

Fordos and Gelis' method, 45 
iieat of formation, 56, 324 
solution, 324 
volatilization, 324 
O. Hertig's method, 47 
Liebig's method, 44 
list of works producing, 74 
methods of manufacture, 81 
simple, 22 
solubility of, 327 
strong solution, 301 
use of, 294 
weak solutions, 302 

Cyanides manufacturing processes* 

Adler's process, 93 

Armengaud's process, 126 

Beilby's process, 162 

Bergmann's process, 94 

Beringer's process, 101, 150 

Blackmore's process, 150 

Blairs' process, 126 

Boussingault's process, 119 

Bower's process, 107 

British Cyanide Co.'s process, 105 

Brunquell's process, 153 

Bueb's process, 185 

Bunsen's process, 123 

Castner's process, 141, 153, 172 

Chaster's process, 88, 165 

Chem. Fabrik Aktiengesellschaft's, 

Chem. Fabrik Pfersee Augsburg, 149 

Chipmann's process, 138 

Conroy's process, 107 

Dalinot's process, 92 

Deutsche Gold u. Silber Scheide 
Anstalt, 175 

Dickson's process, 129 

Dzuik's process, 150 

Etard's process, 110, 120 

Finlay's process, 110 

Fogarty's process, 128 

Frank and Caro's process, 144, 153 

Gen. Elec. Chem. Co.'s process, 152 

Gilmour's process, 134 

Glock's process, 179 

Goerlich and Wichmann's process, 107 

Grossmann's process, 182 

Hetherington and Musspratt's proc- 
ess, 106 

Hood and Salamon's process, 169 

Hornig's process, 170 

Hornig and Schneider's process, 143 

Hoyermann's process, 180 

Huntington's process, 180 

Karmrodt's process, 153 

Kellner's process, 182 

Kerp's process, 181 

Lambilly's process, 129, 161, 178 

Lance and Bourgade's process, 156 

Liebig's process, 87, 153 

Lucas' process, 153 

Luttke's process, 104 

Mackey's process, 135 

Mactear's process, 157 

Mallet's process, 121 

Margueritte and SourdevaFs process, 
126, 153 

Martin's process, 179 

Mehner's process, 137, 143 

Moi'se and Mehner's process, 140 

Mond's process, 127 

Moulis and Sars' process, 160 

Newton's process, 126 



Cyanides manufacturing processes : 
Old processes, 85 
Ortlieb and Miiller's process, 190 
Parkinson's process, 120 
Pestchow's process, 137 
Pictet's process, 121 
Pfleger's process, 165 
Playf air's process, 102 
Possoz and Boissiere' s process, 124 
Raschen and Brock's process, 97, 110 
Readmann's process, 135 
Roca's process, 166 
Rossler and Haaslacher's process, 89 
Roussin's process, 181 
Schneider's process, 171 
Silesia Verein Chem. Fabrik's process, 

Societe Anonyme de Croix's process, 

Stassfurter Chem. Fabrick's process, 


Swan and Kendall's process, 137 
Synthetic processes, 111 
Tessie' du Mothay's process, 120 
Vidal's process, 184 
Villepigne's process, 121 
Wagner's process, 88 
Weldon's process, 128 
Wichmann and Vautin's process, 88 
Wolfram's process, 150 
Young's process, 134 
Young and Macfarlane's process, 163 
Cyaniding mixture, 168 
Cyanogen, constitution of ,5 

conversion tension, 14 

formation, 12 

preparation, 13 

properties, 10 
Cyanosulphite of potassium, 22 

Dalinot's process, hydrocyanic acid, 92 

Deiss and Monnier's process, sulphocya- 
nide, 281 

Deutsche Gold u. Silber Scheide Anstalt's 
process, ferrocyanide, 265 

DeWilde's process, 303 

Donath's process, ferrocyanide, 258 

Donath and Margosche's method, ferrocya- 
nide, 53 

Double cyanides, 28 

Dubosc's process, ferricyanide, 265 

du Castelet Works' process, ferrocyanide, 

Dzuik's process, cyanide, 150 

En^ler's apparatus, 201 
Erlenmeyer's method, ferrocyanide, 49 
Esop's process, ferrocyanide, 258 
Etard's process, hydrocyanic acid, 94 
Ethyl cyanate, 40 
cyanide, 40 

Everitt's process, 16 
Feld's process, ferrocyanide, 241 
Ferricyanide, manufacture of, 261 
of potassium, 43, 32 
Ferricyanide processes : 

Beck's process, 267 

Chlorine process, 261 

Deutsche Gold u. Silber Scheide An- 
stalt's process, 265 

Dubosc's process, 265 

Kassner's process, 266 

Mines at Bouxvillers, 264 

Reichardt's process, 263 

Williamson's process, 267 
Ferricyanide, use of, 319 
Ferrocyanide, 25, 43 

manufacture of, 192, 205, 

Ferrocyanide processes : 

Bower's process, 243 

BrunquelPs process, 210 

Bueb's process, 237 

Glaus s and Domeier's process, 234 

Conroy's process, 212 

Donath's process, 258 

Esop's process, 258 

Feld's process, 241 

Fowlis' process, 233 

Gasch's process, 232 

Gauthier-Bouchard's process, 248 

Goerlich and Wichmann' s process, 213 

Harcourt's process, 257 

Hempel's process, 257 

Hetherington's process, 212 

Holbling's process, 259 

Karmrodt's process, 211 

Knublauch's process, 231 

Kunheim's process, 257 

Lewis' process, 236, 243, 259 

Marasse's process, 258 

Mascow's process, 259 

Musspratt's process, 212 

Pendrie's process, 242 

Richter's process, 258 

Rowland's process, 233 

Schroeder's process, 234 

Teichmann's process, 235 

Valentin's process, 256 

Wolfram's process, 257 

Works du Castelet, 213 
Ferrocyanide, detection of: 

Burchell's method, 52 

Erlenmeyer's method, 49 

Knublauch's method, 50 

Moldenhauer and Leybold's method, 

Ferrocyanide of iron, 31 

potassium, 29 
sodium, 31 

Ferrocyanide, precipitation of, 253 
use of, 316 



Filtering-vats, 300 

Flemming's furnace, 158 

Fordos and Gelis' method, 45 

Formates, detection of, 47 

Frank and Caro's process, cyanide, 144 

Furnaces, Flemming's, 158 
Gruneberg's, 158 
reverberatory, 199 
Siepermann's, 158, 182 

Gas, composition of, 226 

Gasch's process, ferrocyanide, 232 

Gauthier-Bouchard's process, ferrocya- 
nide, 248 

Gelis' process, sulphocyanide, 272 

Gen. Elec.-Chem. Co.'s process, cyanide, 

Goerlich and Wichmann's process, cyanide, 

Goerlich and Wichmann's process, ferrocy- 
anide, 213 

Goerlich and Wichmann's process, sulpho- 
cyanide, 286 

Gold-bromine cyanide, formation, 297 

Gold cyanide, 35 

precipitation of, 298, 304, 314 
solution of, 298 

Grossmann's process, cyanide, 182 

Gruneberg's furnace, 158 

Harcourt's process, ferrocyanide, 257 
HempePs process, ferrocyanide, 257 
Hertig's method, cyanates, 47 
Hetherington's process, ferrocyanide, 212 
Hetherington and Musspratt's process, 

cyanide, 106 

Holbling's process, ferrocyanide, 259 
Hood and Salamon's process, cyanide, 169 

nide, 282 

Hornig's process, cyanide, 170 
Hornig and Schneider's process, cyanide, 


Hydrate of iron, composition, 247 
Hydrocyanic acid, 14, 42 

Buignet's method, 48 
heat of formation, 57 
Hydrocyanic acid: 

Adler's process, 93 

Bergmann's process, 94 

Chaster's process, 88 

Dalinot's process, 92 

Etard's process, 94 

Liebig's process, 87 

Rossler and Haaslacher's process, 89 

Wagner's process, 88 

Wichmann's and Vautin's process, 90 

Illuminating-gas, composition, 226 
elements of, 218 

Karmrodt's process, cyanide, 153 

ferrocyanide, 211 
Kassner's process, ferricyanide, 266 
Keith's process, gold precipitation, 314 
Kellner's process, cyanide, 182 
Kerp's process, cyanide, 181 
Knublauch's process, ferrocyanide, 231 
Kunheim's process ferrocyanide, 257 

Lambilly's process, cyanide, 153, 161 
Laming mixture, composition, 246 
Lance and Bourgade's process,cyanide,156 
Lewis' process, ferrocyanide, 236, 243, 259 
Liebig's method, cyanide, 44 

process, cyanide, 153 

hydrocyanic acid, 87 

theory, 9 

Limonite, composition of, 247 
Lixiviation, 210, 249 
vats, 252 

Lucas' process, cyanide, 153 
Luttke's process, cyanide, 104 
Lux mass, composition, 246 

MacArthur and Forrest's method, 304 1 
Mackey's process, cyanide, 135 
Mactear's process, cyanide, 157 
Manganese cyanides, 25, 34 
Marasse's process, ferrocyanide, 258 
Margueritte's process, cyanide, 153 
Margueritte and SourdevaFs process, cya- 
nide, 126 

Martin's process, cyanide, 179 
Mascow's process, ferrocyanide, 258 
Mehner's process, cyanide, 143 
Melam, 39 
Mercury cyanide, 26 
Metal, production of, 197 
Metallic cyanides, 18 
Methyl cyanate, 46 
cyanide, 40 

Moise and Mehner's process, cyanides, 140* 
Moldenhauer and Leybold's method, 51 
Mond's process, cyanide, 127 
Monthier's blue, 292 
Moulis and Sars' process, cyanide, 160 
Mulholland's process, 303 
Musspratt's process, ferrocyanide, 212 

Newton's process, cyanide, 126 
Nickel cyanide, 27 

ferricyanide, 32 
Nitriles, 39 
Nitroferricyanides, 35 
Nitroprussiates, 35 
Non-synthetic processes, 85 

Old process, cyanide, 85 

ferrocyanide, 193 
Organic compounds, 39 
Ortlieb & Miiller's process, cyanide, 190' 



Oxide of iron, composition of, 247 
Oxygen compounds of cyanogen, 36 

Paracyanogen, 13, 147 
Pendrie's process, ferrocyanide, 242 
Pfleger's process, cyanide, 165 
Physical study cyanogen, 10 
Platinum cyanide, 27 
Platino cyanides, 34 
Playfair's process, cyanide, 102 
Potash, determination of, 48 
Potassium cyanate, 36, 60 
cyanide, 20, 58 

analysis of, 47 
antidote, 22 
heat of formation, 58 
manufacture, 85 
production, 72 
use of, 70 
cyaniferride, 32 
cyanosulphite, 21 
ferricyanide, 32 

production, 72 
ferrocyanide, 29, 43, 49 

exportation, 80 
heat of forma- 
tion, 60 

importation, 79 
production, 72 
sulphide, detection, 47 
sulphocyanide, 38 
Processes utilizing ammonia, 153 

atmospheric nitrogen, 


Propionitrile, 40 
Propyl cyanide, 40 
Prussian blue, 31 

determination, 54 
discovery of, 69 
manufacture, 288 
use of, 319 

Woodward's method, 289 
Prussic acid, 14 

action on system, 17 
antidote, 18 
Purifying materials, 50 

composition, of, 219, 

226, 245 
revivification, 247 

Raschen' s apparatus, 99 
Raschen and Brock's method, 97 
Raschen, Davidson and Brock's process, 

cyanide, 110 

Readmann's process, cyanide, 135 
Red prussiate of potash, 32 
Reichardt's process, ferricyanides, 263 
Retort, 198 
Rhodanides, 37 

Richter's process, ferrocyanides, 258 
Roca's apparatus, 167 

process, cya- 

Roca's process, cyanide, 166 
Rossler and Haaslacher's process, hydro- 
cyanic acid, 89 

Roussin's process, cyanides, 181 
Rowland's process, ferrocyanide, 233 

Schneider's process, cyanide, 171 
Schroeder's process, ferrocyanide, 234 
Siemens and Halske's process, gold pre- 
cipitation, 314 

Siepermann's furnace, 158, 182 
Silesia Verein Chem. Fabrik's pr 

nide, 107 
Silver cyanate, 37 
cyanide, 26 
ferricyanide, 32 
Simple cyanide, formation, 19 
properties, 19 

Socie'te' Anonyme de Croix's process, cya- 
nide, 190 

Sodium cyanate, 37 
cyanide, 23 
ferrocyanide, 31 
Soluble Prussian blue, 32, 292 
Sourdeval's process, cyanide, 153 
Spent oxide, 54 

composition, 246 

Stassfurter Chem. Fabrik's process, cya- 
nide, 158 

Sulman's process, 303 
Sulphate of iron, composition of, 247 
Sulphocarbamide, 39 
Sulphocyanates, 37 
Sulphocyanide, 37, 43, 50 
cost of, 271 
detection of, 47 
manufacture, 269 
Sulphocyanide processes : 
Albright's process, 285 
British Cyanide Co.'s process, 283' 
Brock's process, 282 
Deiss and Monnier's process, 281 
Gelis' process, 270 

Goerlich and Wichmann's process, 286'- 
Hood and Salamon's process, 282 
Tcherniac's process, 285 
Sulphocyanide recovery, 56 

use of, 319 

Swan and Kendall's process, cyanide, 137 
Synthetic processes, cyanide, 111 

Tables, 294 

Tar, 218 

Tcherniac's process, sulphocyanide, 285 . . 

Teichmann's process, ferrocyanide, 235 , 

Tin cyanide, 25 

Thomson's process, 16 

Toxicological research, 54 

Tricyanates, 37 i 

TurnbulPs blue, 33, 292 

Valentin's process, ferrocyanide, 256: * 



Vats, filtering, 299 
Vauquelin's process, 16 
Vidal's process, cyanide, 184 

Wagner's process, cyanide, 88 
Weldon's process, cyanide, 127 
Wichmann and Vautin's process, cyanide, 


Williamson's process, ferricyanide, 267 
Wolfram's process, cyanide, 150 

Wolfram's process, ferrocyanide, 257 
Woodward's method, 289 

Young's process, cyanide, 134 
Young and Macfarlane's process, cyanide, 

Zaloziecki's method, ferrocyanide, 52 
Zinc cyanide, 24 

potassium cyanide, 22 








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